How many multiples of 21 are there between 200 and 400?

Question

How many multiples of 21 are there between 200 and 400?

Answer 1

We want all integers, n, for which the following inequality is true:

 

200 ≤ 21*n ≤ 400

 

200/21 ≤ n ≤ 400/21

 

9.52 ≤ n ≤ 19.05

 

Since n must be an integer:

 

10 ≤ n ≤ 19

 

The answer is 10 multiples of 21:

 

21*10, 21*11, 21*12, ..., 21*19