Question
Question: All possible two factors product are formed from numbers 1, 2, 3, 4, .... 200. The number of factors...
All possible two factors product are formed from numbers 1, 2, 3, 4, .... 200. The number of factors out of the total obtained which are multiples of '5' is
A
5040
B
7180
C
8150
D
None of these
Answer
7180
Explanation
Solution
Total two factors product = 200C2
For multiple of 5 at least one of the factor must be from 5, 10, 15, .... 195
Two factors product which are
not multiple '5' = 160C2
multiple of '5' = 200C2 – 160C2 = 7180