The probability of the product of 3 numbers chosen from the set A = {1,2,3,4,……20} is divisible by 4 is equal to

The 3 numbers whose product is not divisible by 4 can be chosen in
(i) all odd
(ii)two odd and one even
Which is not a multiple of 4 it can be done in ${10}_{C_3}+{10}_{C_2}\times 5_{C_1}=345$  ways.
So required probability =  $\frac{20C_3-345}{{20}_{C_3}}=\frac{53}{76}$