25 How many integers between 1 and 1400 are divisible by eit

25. How many integers between 1 and 1400 are divisible by either 2 or 7 ?

Solution

number of integers which are divisible by 2 =1400/2 = 700

number of integers which are divisible by 7 = 1400/7 = 200

number of integers which are divisible by both 2,7(i.e divisible by 14) = 1400/14= 100

=>

number of integers which are divisible by 2 or 7 = 700 +200 -100 = 800