Question

what percentage of numbers from 1 to 70 has 1 or 9 in the unit's digit?

A.19%
B.14%
C.20%
D.21%

please answer in detail.

Answer 1

here we have total number equal to 70
and desired numbers at the unit place are 1 or 9
therefore total possible way of filling the unit place is 2
and total possible way of filling the tens place is 7 (1 to 7)
therefore total possible ways that 1 or 9 is at unit place is
=2*7
=14
therefore percentage equal to
=14*100/70
=20%