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MONEY


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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.

 

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2 hours ago, flamebirde said:
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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!

 

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7 hours ago, ThunderCloud said:

Hmmm, I'll go for the seemingly obvious…

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8 ?

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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!

 

 

 

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Sorry ... nobody said 9! Didn't read carefully!!!

 

10 minutes ago, rocdocmac said:
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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!

 

 

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14 hours ago, ThunderCloud said:

Hmmm, I'll go for the seemingly obvious…

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8 ? 

NIIICE

 

 

13 hours ago, flamebirde said:
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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

 

 

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