Question

Find the sum of the number lying between 1 and 200 which are not divisible by 3 or 7

Answer 1

Consider numbers 2 to 199.

Numbers divisible by 3 =

3*1=3, 3*2=6, …3*66=+198

So 66 multiples of 3.

Numbers divisible by 7 =

7*1=7, 7*2=14, ….., 7*28= 196

So 28 multiples of 7.

Numbers divisible by (3*7=21 are

= 21*1=21, 21*2=42, … 21*9= 189

So 9 multiples of 21.

Answer = Numbers divisible by 3 or 7

= (66+28)-9 = 85 such numbets.

Answer 2

Answer:

85 number are lying between 1 to 200 which are not divisible by 3 or 7