Question

how many letters are there between 400 and 1000 that are divisible by both 5 and 7?​

Answer 1

Answer:

Step-by-step explanation:

LCM of 5,7 = 35

if the number is divisable by 35, it is automatically divisable by 5,7.

First divisable number = 420

Last divisable number = 980

420,455,490,..............,980.

This is in the form of AP.

a1=420,d=35

Last term in the series an=980

a1+(n-1)d=980

420+(n-1)35=980

(n-1)35=980-420

n-1=560/35

n-1=16

n=17

Total divisable numbers between 400 and 1000 = 17