I always try 0 Posted April 4, 2018 Report Share Posted April 4, 2018 My goal is to have $12. If I save $1 a month then it will take me 12 months to save $12. If I save $2 a month then it will take me 6 months to save $12. What if I saved $1.50 each month? How many months would it take me to save $12? Cmon try to solve Quote Link to post Share on other sites

1 Solution rocdocmac 9 Posted April 5, 2018 Solution Report Share Posted April 5, 2018 7 hours ago, ThunderCloud said: Hmmm, I'll go for the seemingly obvious… Hide contents 8 ? Spoiler I tend to agree with 8. If the problem is exponential and not linear, how come "9" is right in the middle between 6 and 12? After all, 12*1 = 12, 6*2 = 6, and 8*1.5 = 12, whereas 9*1.5 = 13.5! Spoiler Sorry ... nobody said 9! Didn't read carefully!!! 10 minutes ago, rocdocmac said: Spoiler I tend to agree with 8. If the problem is exponential and not linear, how come "9" is right in the middle between 6 and 12? After all, 12*1 = 12, 6*2 = 6, and 8*1.5 = 12, whereas 9*1.5 = 13.5! Quote Link to post Share on other sites

1 flamebirde 196 Posted April 5, 2018 Report Share Posted April 5, 2018 Spoiler The trick answer's 9 months. Because if 1 dollar is 12 months, and 2 dollars is six months, then 1.50 is in the middle of those two, so surely the time also has to be in the middle of the time span. The number in the middle of 12 and 6 is 9, so 9 months. However, what's important to note is that this problem isn't linear but exponential. That is, the change in time spent saving is much greater when we go from $1 to $2 than it is when we go from $6 to $7. So originally from $1 to $2, we double our initial savings amount, so we halve the time it takes. From $1 to $1.50, though, we increase our savings amount by 50%, so the total time it'll take is 12/(1.5)=8 months. Of course, the simple way to do it is just to divide 12 dollars by 1.5 dollars a month, but the above answer gives a little more reasoning to it. Quote Link to post Share on other sites

0 ThunderCloud 5 Posted April 5, 2018 Report Share Posted April 5, 2018 Hmmm, I'll go for the seemingly obvious… Spoiler 8 ? Quote Link to post Share on other sites

0 ThunderCloud 5 Posted April 5, 2018 Report Share Posted April 5, 2018 2 hours ago, flamebirde said: Hide contents The trick answer's 9 months. Because if 1 dollar is 12 months, and 2 dollars is six months, then 1.50 is in the middle of those two, so surely the time also has to be in the middle of the time span. The number in the middle of 12 and 6 is 9, so 9 months. However, what's important to note is that this problem isn't linear but exponential. That is, the change in time spent saving is much greater when we go from $1 to $2 than it is when we go from $6 to $7. So originally from $1 to $2, we double our initial savings amount, so we halve the time it takes. From $1 to $1.50, though, we increase our savings amount by 50%, so the total time it'll take is 12/(1.5)=8 months. Of course, the simple way to do it is just to divide 12 dollars by 1.5 dollars a month, but the above answer gives a little more reasoning to it. Clever. ^^; Nice explanation! Quote Link to post Share on other sites

0 I always try 0 Posted April 5, 2018 Author Report Share Posted April 5, 2018 14 hours ago, ThunderCloud said: Hmmm, I'll go for the seemingly obvious… Hide contents 8 ? NIIICE 13 hours ago, flamebirde said: Hide contents The trick answer's 9 months. Because if 1 dollar is 12 months, and 2 dollars is six months, then 1.50 is in the middle of those two, so surely the time also has to be in the middle of the time span. The number in the middle of 12 and 6 is 9, so 9 months. However, what's important to note is that this problem isn't linear but exponential. That is, the change in time spent saving is much greater when we go from $1 to $2 than it is when we go from $6 to $7. So originally from $1 to $2, we double our initial savings amount, so we halve the time it takes. From $1 to $1.50, though, we increase our savings amount by 50%, so the total time it'll take is 12/(1.5)=8 months. Of course, the simple way to do it is just to divide 12 dollars by 1.5 dollars a month, but the above answer gives a little more reasoning to it. Oops that's 8 Quote Link to post Share on other sites

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## I always try 0

My goal is to have $12. If I save $1 a month then it will take me 12 months to save $12. If I save $2 a month then it will take me 6 months to save $12. What if I saved $1.50 each month? How many months would it take me to save $12?

Cmon try to solve

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