[ARCHIVED THREAD] - 4th grade math problem (Page 1 of 2)
Posted: 10/7/2013 7:38:49 PM EDT
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for #9 does the first sentence make sense? 'use the rule is that each....'????
obviously math isnt my strong suit help with a solution would be appreciated! 
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so they are supposed to figure out the proper grammar for the question, and ignore the poor wording to build a table containing a negative number before they get the final answer? 0 x 3 - 1 = -1 1 x 3 - 1 = 2 2 x 3 - 1 = 5 3 x 3 - 1 = 8 at least that's how i read it. In the new math there may actually be no wrong answers. so the kid get a A for effort. |
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That's retarded, sir.
The sentence makes no sense. If it was "Use the rule that each number is one less than three times the PREVIOUS number" it would make sense. Else it's asking for each number that is one less than three times itself. That number is .5 It's the only one that fits the description. |
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the equation is 3x-1..
1) 3(1)-1=2 2) 3(2)-2=4 3) 3(3)-1=8 4) 3(4)-1=11 im guessing 11 because it didnt tell you to start with a specific number (x) which they should have done.. ETA: since the multiplication chart does have 0 im going to edit to start at 0 for x.. 1) 3(0)-1=-1 2) 3(1)-2=1 3) 3(2)-1=5 4) 3(3)-1=8 |
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This is all sorts of fucked up.
There is no pattern. What is given is an equation: ETA: Which is not the same as the sequence defined by: The second is probably what they are asking for, but there still no correct number, as there is no starting value for their "pattern." Presumably, they want either Tell your kid's teacher that he or she needs better handouts. Also, I'm relatively sure that my notation is right, but somebody with a math class in the last decade might want to double check me. |
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This is grossly wrong. |
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This is grossly wrong. Quoted:
This is grossly wrong. 
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1x3=3 3-1=2 2x3=6 6-1-5 3x3=9 9-1=8 4x3=12 12-1=11 4th # for this pattern is 11 It appears that there are many answers dependant on the number that the person uses to start the pattern and the string that follows. Same here. In this particular context, I don't think neg #'s are part of std 4th grade curriculum, so starting at 1 to avoids that. |
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Same here. In this particular context, I don't think neg #'s are part of std 1st grade curriculum, so starting at 1 to avoids that. Quoted:
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1x3=3 3-1=2 2x3=6 6-1-5 3x3=9 9-1=8 4x3=12 12-1=11 4th # for this pattern is 11 It appears that there are many answers dependant on the number that the person uses to start the pattern and the string that follows. Same here. In this particular context, I don't think neg #'s are part of std 1st grade curriculum, so starting at 1 to avoids that. That is why this......f(x)=3x-1 ...... is the correct and complete equation. |
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Same here. In this particular context, I don't think neg #'s are part of std 1st 4th grade curriculum, so starting at 1 to avoids that. Quoted:
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1x3=3 3-1=2 2x3=6 6-1-5 3x3=9 9-1=8 4x3=12 12-1=11 4th # for this pattern is 11 It appears that there are many answers dependant on the number that the person uses to start the pattern and the string that follows. Same here. In this particular context, I don't think neg #'s are part of std 1st 4th grade curriculum, so starting at 1 to avoids that. as the title states, its a 4th grade level problem. I believe i started learning about negative integers in the 3rd grade.. but you are right about the answer being dependant on the specific number to start the pattern and the following string |
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Why are you summing anything? Also,a sum is written like this: But more importantly, your expression adds a couple of sums in for no reason. What you are doing is: minus which equals 8. That's potentially one of the correct answers to what the problem really wanted. But the way you got it doesn't make any sense. You effectively said (1+2+3+4)-(1+2+3)=4. It added a lot of steps that were unnecessary. Quoted:
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Same here. In this particular context, I don't think neg #'s are part of std 1st grade curriculum, so starting at 1 to avoids that. That is why this......f(x)=3x-1 ...... is the correct and complete equation. Except you don't have any reason to begin at either zero or one. All the original problem said is that ETA: There is no pattern. The rule that is given--"each number is one less than three times the number"--is satisfied by exactly one number. 0.5. That's it. There are no other numbers that satisfy the rule as written. |
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Yeah the parentheses around each sum are implied.
I also wrote it like that because I couldn't remember the notation for the n-th place of a sequence, other than to just say the value of the series at the n-th place minus the value of the series at the n-1 place. 
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Should I bother pointing out that the answers to 6 and 7 are wrong? 
For six (multiples of 11) they are looking for the answer that each digit increases by 1 as you increase each multiple. For example, to go from 33 to 44, you increase both the tens and ones number by one. For seven (multiples of 9) they are looking for the answer that the tens digit increases by one and the ones digit decreases by one. They want to know the pattern that you see, not if you can copy the numbers out of the table. For question 9, delete the word "is" and it will (hopefully) make sense. |
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OP, grammatically speaking, there is either an unneeded "is" in that sentence, or a missing set of quotes.
Use "the rule is that each number is 1 less than 3 times the number" to make a pattern...... Still kind of nonsensical the second way, so I'd bet that it's and "is" typo. |
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Yeah the parentheses around each sum are implied. I also wrote it like that because I couldn't remember the notation for the n-th place of a sequence, other than to just say the value of the series at the n-th place minus the value of the series at the n-1 place. You are confusing sequence and series. There is no reason to sum anything at all for this question. |
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OP, grammatically speaking, there is either an unneeded "is" in that sentence, or a missing set of quotes. Use "the rule is that each number is 1 less than 3 times the number" to make a pattern...... Still kind of nonsensical the second way, so I'd bet that it's and "is" typo. Even ignoring the "is" the problem is meaningless. No pattern exists. There is exactly one solution (x=1/2). There is no fourth number in the pattern, because there is neither a pattern nor a fourth number. |
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Even ignoring the "is" the problem is meaningless. No pattern exists. There is exactly one solution (x=1/2). There is no fourth number in the pattern, because there is neither a pattern nor a fourth number. Quoted:
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OP, grammatically speaking, there is either an unneeded "is" in that sentence, or a missing set of quotes. Use "the rule is that each number is 1 less than 3 times the number" to make a pattern...... Still kind of nonsensical the second way, so I'd bet that it's and "is" typo. Even ignoring the "is" the problem is meaningless. No pattern exists. There is exactly one solution (x=1/2). There is no fourth number in the pattern, because there is neither a pattern nor a fourth number. FACEPALM.JPG |
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Even ignoring the "is" the problem is meaningless. No pattern exists. There is exactly one solution (x=1/2). There is no fourth number in the pattern, because there is neither a pattern nor a fourth number. Quoted:
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OP, grammatically speaking, there is either an unneeded "is" in that sentence, or a missing set of quotes. Use "the rule is that each number is 1 less than 3 times the number" to make a pattern...... Still kind of nonsensical the second way, so I'd bet that it's and "is" typo. Even ignoring the "is" the problem is meaningless. No pattern exists. There is exactly one solution (x=1/2). There is no fourth number in the pattern, because there is neither a pattern nor a fourth number. I think this 4th grade problem is kicking your ass. You're over thinking it and you are solving an equation that does not apply while missing what the question is actually asking. |
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I think this 4th grade problem is kicking your ass. You're over thinking it and you are solving an equation that does not apply while missing what the question is actually asking. Quoted:
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OP, grammatically speaking, there is either an unneeded "is" in that sentence, or a missing set of quotes. Use "the rule is that each number is 1 less than 3 times the number" to make a pattern...... Still kind of nonsensical the second way, so I'd bet that it's and "is" typo. Even ignoring the "is" the problem is meaningless. No pattern exists. There is exactly one solution (x=1/2). There is no fourth number in the pattern, because there is neither a pattern nor a fourth number. I think this 4th grade problem is kicking your ass. You're over thinking it and you are solving an equation that does not apply while missing what the question is actually asking. No, I'm really not. You are adding in information that you think should be there in order to solve the problem that you think they should be asking. You're probably right about what they want to be asking, but the way it is written, there is one, and only one, solution. |
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Write a pattern that fits the rule, then tell what the 4th number equals. 1, (1*3)-1= 2, (2*3)-1= 5, (5*3)-1=14. That's what I was tracking - the pattern applies to the previous number, not the whole set of integers. Still need a starting point, though. But, if zero, you would jump right into negative numbers. Hey OP - FWIW, the pattern for the 9s and 11s is not just a list of numbers. Help your daughter out there. All multiples of 9 are adding up to 9 (when they don't the product of those numbers are 9). Multiples of 11 are the number, twice. Then, once you hit two digits, the digits split and the number in the middle is the sum of those digits. It's a pretty basic pattern, and I think that's what they want your kid to catch on to. |
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To illustrate what you are doing wrong:
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This. Quoted:
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f(x)=3x-1 f(1)=2 f(2)=5 f(3)=8 f(4)=11 .. .. .. This. Your belief is that the "pattern" being sought in the original question is an infinite sequence (2,5,8,11,14,...), correct? The problem with this is that the question would then have to read "the rule is 1 less than 3 times than the number's position in the sequence," which mathematically we would write as You're also assuming that their "pattern" is based on the sequence beginning with f(1), when it is just as likely to be f(0) or f(17493). You can't make up your own parameters for the question when they are not provided. The way the question is written--"each number is 1 less than 3 times the number"--is easily written mathematically. "Number" is unknown. x=3x-1. That is solvable, and results in only one solution. I suppose you could populate a sequence with possible solutions for that equation. It would look like (1/2). If you don't believe me, pick a number at random to plug into the problem as it is written. Let's pick 87. "87 is 1 less than 3 times 87" is what we wind up with. It is obviously false. The only number that satisfies the problem is 1/2. |
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To illustrate what you are doing wrong: Your belief is that the "pattern" being sought in the original question is an infinite sequence (2,5,8,11,14,...), correct? The problem with this is that the question would then have to read "the rule is 1 less than 3 times than the number's position in the sequence," which mathematically we would write as http://latex.codecogs.com/gif.latex?%5C%5C%20f_n%3Df_3_n_-_1 You're also assuming that their "pattern" is based on the sequence beginning with f(1), when it is just as likely to be f(0) or f(17493). You can't make up your own parameters for the question when they are not provided. The way the question is written--"each number is 1 less than 3 times the number"--is easily written mathematically. "Number" is unknown. x=3x-1. That is solvable, and results in only one solution. I suppose you could populate a sequence with possible solutions for that equation. It would look like (1/2). If you don't believe me, pick a number at random to plug into the problem as it is written. Let's pick 87. "87 is 1 less than 3 times 87" is what we wind up with. It is obviously false. The only number that satisfies the problem is 1/2. Quoted:
To illustrate what you are doing wrong: Quoted:
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f(x)=3x-1 f(1)=2 f(2)=5 f(3)=8 f(4)=11 .. .. .. This. Your belief is that the "pattern" being sought in the original question is an infinite sequence (2,5,8,11,14,...), correct? The problem with this is that the question would then have to read "the rule is 1 less than 3 times than the number's position in the sequence," which mathematically we would write as http://latex.codecogs.com/gif.latex?%5C%5C%20f_n%3Df_3_n_-_1 You're also assuming that their "pattern" is based on the sequence beginning with f(1), when it is just as likely to be f(0) or f(17493). You can't make up your own parameters for the question when they are not provided. The way the question is written--"each number is 1 less than 3 times the number"--is easily written mathematically. "Number" is unknown. x=3x-1. That is solvable, and results in only one solution. I suppose you could populate a sequence with possible solutions for that equation. It would look like (1/2). If you don't believe me, pick a number at random to plug into the problem as it is written. Let's pick 87. "87 is 1 less than 3 times 87" is what we wind up with. It is obviously false. The only number that satisfies the problem is 1/2. 
You are writing a pattern. One where the subsequent number is one less than three times the previous number. I think even most 4th graders can grasp that concept. Here is a website written Barney-style: http://www.mathsisfun.com/algebra/sequences-finding-rule.html |
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You are writing a pattern. One where the subsequent number is one less than three times the previous number. I think even most 4th graders can grasp that concept. Here is a website written Barney-style: http://www.mathsisfun.com/algebra/sequences-finding-rule.html That would be precisely correct, if those parameters were given. They were not. Show me, in the original problem, where it says anything about subsequent numbers or previous numbers, and where it says anything about the relationship between two different numbers. You are pulling extra parameters out of your ass to satisfy the problem that you think they want to ask. The question as written is the same as saying "use the rule that each number is 7 to make a pattern." It's meaningless. Your link is nice. It's also useless. There is no sequence from which to derive a rule, because there is only one number in the sequence. Just out of curiosity, what is your background in mathematics? |