The number of digits in the number N=2^12×5^8 is:

1971 AMC 12 Problem 1

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The number of digits in the number

N=2^{12}\times5^8

is:

9

10

11

12

20

Pair as many factors of

2

and

5

as possible

Rewrite the number as

2^4\cdot10^8

We have

2^{12}5^8=2^4(2^85^8)

and

16\cdot10^8=1{,}600{,}000{,}000,

which has

10

digits.

Therefore, the correct answer is B.