Brain Teasers
Tom and John
The sum of the ages of Tom and John is 20 years. In 4 years, John's age will be three-fourths of Tom's age. How old is Tom now?
Answer
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ok... I calculated Tom to be 11.4 and John to be 8.6 (but I rounded them to be 11 and 9) wanna tell me what I did wrong?
Adding 4 for each of the 2 boys, 4 years from now their ages' sum will be 28. At that future time, 28 = seven-fourths of Tom's future age.
28 / (7/4) = (28/7) * 4 = 4 * 4 =16. Subtract 4 and learn that Tom's current age is 12.
It's a Sh-Sh-Sh-Shame that the editor's still accept any age questions as new teasers. Changing a couple of names and some numbers does not change the basic point of the question, a question which is only a tease of sorts while you learn algebra.
28 / (7/4) = (28/7) * 4 = 4 * 4 =16. Subtract 4 and learn that Tom's current age is 12.
It's a Sh-Sh-Sh-Shame that the editor's still accept any age questions as new teasers. Changing a couple of names and some numbers does not change the basic point of the question, a question which is only a tease of sorts while you learn algebra.
That was too easy
Even easier than Stil's method: the ratio of the two at a total of 28 is 3::4 so 28/(3+4) = 4. Tom is 4x4=16 in four years, so he's 12 now.
I agree there are too many similar (and uninteresting) "teasers" getting approved.
I agree there are too many similar (and uninteresting) "teasers" getting approved.
extremely simple, but fun.
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