FILE No.106Unsolved
An elementary school teacher gave a problem to a third-grade class. "Take just one quick look at this problem." It was a multiplication of 100 assorted numbers in a row. The teacher said, "Even you can solve it right away."
One student answered, "Solved it," in about 10 seconds. The student is no special genius. The 100 numbers are all different, and some have two or three digits. It was the first time the student had seen this problem.
How did the student solve it?
If you get stuck, open the hints one at a time, in order.
Do you really need to calculate every number?
What if a special number were mixed in?
Think about what "take one quick look" means.
How did the student solve it?
Choose the answer closest to the truth.
Because the student noticed a 0 was in the list
The answer is "Because the student noticed a 0 was in the list."
If a multiplication contains a 0, the answer is 0. It does not matter what the other 99 numbers are.
Even a mental-math expert cannot multiply 100 numbers in 10 seconds. It does not say the numbers are all the same. And because the teacher said "even you," no special knowledge is needed.
Because you try to multiply the 100 numbers one by one and get overwhelmed.
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