Sunday, July 23, 2006

The case of the missing 10 cents

Suppose Ali, Bala, and John buy a ruler that costs $2.50. They each have $1, and they pool a total of $3 to purchase the latter. So the change is 50 cents. Now, if we give each boy 10 cents back (since we cannot split 50 cents evenly among the 3 boys), we would have 20 cents left. But by doing so, each boy would have contributed 90 cents. In all, they contribute 90 X 3 = $2.70. If I add back the leftover 20 cents, we would have

$2.70 + $0.20=$2.90.

So where did the 10 cents go?


At 4:39 AM, Blogger Da vidz said...

The error comes from "...If I add back the leftover 20 cents..."

Yes, the 3 boys did contribute $0.90 each, ie $2.70 in total. But it already comprised of the $2.50 ruler and the $0.20 tip. So no need to add the tip again. The remaining $0.30 was back to each of the 3 boys.

At 9:29 AM, Blogger tradingdiary said...

it should be interpreted this way:

Each pay $0.90 and the total sum will be $2.70. After paying for the $2.50 ruler, they have $0.20 left, that is perfectly logical.


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