Question

How many numbers from 0 to 999 are not divisible by either 5 or 7 ? 

(a) 313 (b) 341 (c) 686 (d) 786

Answer 1

(c) Numbers from (0 – 999) divisible by 7,

Numbers from (0 – 999) divisible by 5,

There are few numbers which are divisible by both 5 and 7, i.e., by 35.

Numbers from (0 – 999) divisible by 35,

Numbers divisible by 5 or 7 = 142 + 199 – 28 = 313 

Hence, total numbers between (0 – 999) not divisible by 5 or 7 = 999 – 313 = 686