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

Answer 1

a) first find how many numbers are divisible by 5 and 7 separately add them and subtract that are divisible by both 7 and 5 ie 35.the result subtract from 1000 to get the answer to your first question

nos. divisible by 5 . last no. div by 5 is 995 .hence we have 995 = 0 + ( n-1) 5 which gives 200 .

last no div by 7 is 994 .hence 994 = 0+ ( n-1) 7 which gives n = 143 .

nos div by both 5 and 7 .last no div by 35 is 980.

980 = 0+ (n-1) 35 which gives n= 29

hence there are 200+ 143- 29 = 314 numbers div by 5 or 7

a) not div by 5or 7 = 1000- 314 = 686

b)div by 5 and7 =29

c) div by 5 or 7 = 314

d) div by 5 and not by 7 = 200-29 = 171

so answer is 686

Amit singh