Hi,
The problem description is in the comments above the solution below.

The problem belongs to Codility, you can try out it yourself on their platform.
 

/**
 * that, given three integers A, B and K, returns the number of integers within the range [A..B] that are divisible by K, i.e.:
 *
 *     { i : A ≤ i ≤ B, i mod K = 0 }
 *
 * For example, for A = 6, B = 11 and K = 2, your function should return 3, because there are three numbers divisible by 2 within the range [6..11], namely 6, 8 and 10.
 */
public class CountDiv {
    public int solution(int A, int B, int K) {
        return (B/K - (int)Math.ceil(A/(float)K))+1;
    }
}

Thanks