Question
If 525k is a perfect square, find the smallest possible integer value of k.
Answer
Use prime factorisation or number triangle method first for 525 and we will get 525 = 5 x 5 x 21, next
525k = 5^2 x 21 x k
To make 525k as a perfect square, k must be 21 so that 21 x k = 21 x 21 = 21^2.
This topic is very common in recent years "O" level E. Maths exam.