Question

Find the natural numbers less than 400 and which is not divisible by 17 or 25

Answer 1

17,34,......391 multiples of 17 This form an AP where a=17 d=17

a n=a+(n-1)d

391=17+(n-1)17

391=17(1+n-1)

391÷17=n n=23

25,50,......375multiples of 25 a=25 d=25

375=25+(n-1)25

375÷25=n n=15

so there are 23+15 =38 numbers which are divisible by 17 or 25

400-38=362 and 362 numbers which are not divisible by 17 or 25

hope it helps you thanks