Question

How many divisors of ${10}^5$ end with one zero?

• A. 1
• B. 3
• C. 9
• D. 16

Answer 1

The correct option is C 9

${10}^5=2^5\times 5^5$
Now, all the factors of ${10}^5$ that will end in one zero will have one power of 2 and (1-5) powers of 5 and vice versa.
This will be equal to 10 - 1 = 9. (Minus 1 because in this counting 10 will be counted twice.)