Question

a number is selected at random from first 100 whole numbers.find the probability that the number is divisible by 8 or 12.

Answer 1

answer is : 1/5

Solution :
total numbers which are divisible by 8 is: 12
because 12*8=96 , so 13th number will exceed 100
that's why probability for it is -
12C1/100C1
= 12/100

now, total numbers which are divisible by 12 is: 8 because 8*12=96 , so 13th number will exceed 100
that's why probability for it is -
8C1/100C1
= 8/100
total probability = 12/100 + 8/100
= 20/100
= 1/5