63 and 65 will do it, but I have no idea how to figure it out mathematically.
Since the result ends in a 5, one of the multipliers must end in a 5, but other than that I don't know how to find the answer mathematically.
0 Replies
aidan
2
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Wed 3 Mar, 2010 02:26 pm
@Dorothy Parker,
Well, you know that at least one of the multipliers has to have a 5 in the one's place because your product is a multiple of 5. So one of your multipliers has to be either 55 or 65 because those are the only two whole numbers that fit the criteria between 50 and 70. So I divided 4095 by 65 and got 63.
I knew 55 wouldn't work because there's no number lower than 70 by which you could multiply 55 that would give you a product as high as 4,095 (or even 4,000 which is what I rounded it off to in my head when I was thinking about which of the two possible options made more sense).
good, but that doesn't mean that dp's daughter would know that intuitively.
Could be - although if she's in fourth or fifth grade, she may have been taught how to estimate, and that's one of the important steps in considering possibilities for solving a problem such as this. But you're right - she may not have known how or to do that intuitively. I was just explaining why I chose to divide by 65 instead of 55. Maybe she'll read that or DP will explain it to her- that sort of logic will help her with problems like these in the future.
0 Replies
oolongteasup
1
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Thu 4 Mar, 2010 03:37 am
@Dorothy Parker,
i suspect the answer is untenable
0 Replies
Dorothy Parker
1
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Mon 8 Mar, 2010 02:07 pm
Unfortunately, I am unable to explain the working out of this maths problem. Even if I were to re-read it a hundred times, I would still not understand it. I have never been any good at maths. It used to reduce me to tears at school cos I just could not get my head round certain things.
God knows how I will help her with the maths homework when she's at high school.
People I used to teach, were usually older than DP's daughter..
0 Replies
georgeob1
1
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Mon 8 Mar, 2010 03:42 pm
@Francis,
Yes it does. I merely ommited the tedious detail, which in your Gallic (almost Germanic) thoroughness, you insisted on including. My explanation hit all of the essential ideas.
Well, you know that at least one of the multipliers has to have a 5 in the one's place because your product is a multiple of 5. So one of your multipliers has to be either 55 or 65 because those are the only two whole numbers that fit the criteria between 50 and 70. So I divided 4095 by 65 and got 63.
Mine is second best. I forgot about the 50 & 70 limits and just looked for numbers close to 65. However didn't have the inspired insight to divide by 65.
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