Is a two-digit number divisible by 5 ?
I.The sum of the two digit of the number is 7.
II. The product of the two digits of the number is 10.
From I and II, Let the two digits of the number be x and y Now, x + y = 7 and xy = 6100 (x – y)² = (x + y)² - 4xy = 7² - 4 × 10 = 49 - 40 = 9 ∴x-y = ±3 Thus, we get x = 5 and y = 2 x = 2 and y = 5 The number could therefore be 52 (not divisible by 5) or 25(divisible by 5).