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Tip #2
Annie had an aquarium, and was selling her fish to a pet store. One week she sold half
her supply. The next week, half of that. The next week, half of that amount. She did this
for four weeks. What number could she have started with?
a). 30
b). 60
c). 100
d). 32
e). 12
______________
You could do this by trying each of the answer choices, but think about it a
moment. She can’t sell part of a fish, so we have to be sure that the number each
week is a whole number, that is, not a fraction or decimal. So that means the original
number times 1/2 X 1/2 X 1/2 X 1/2 must be a whole number, which will be
true if it is a multiple of 2 X 2 X 2 X 2, or 16. The only number in the
list which satisfies this is d). 32.
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