Q. If 7 * 24 = 25 and 12 * 16 = 20, then what is 16 * 63 equal to?
(a) 70
(b) 66
(c) 65
(d) 64
UPSC Prelims 2025 CSAT
Explanation :
1. Recognize that in both given examples the two numbers form a Pythagorean-triple leg pair:
– 7² + 24² = 49 + 576 = 625 = 25² ⇒ 7 * 24 = 25
– 12² + 16² = 144 + 256 = 400 = 20² ⇒ 12 * 16 = 20
2. Apply the same rule to 16 * 63:
– Compute 16² + 63² = 256 + 3969 = 4225
– Take the square root: √4225 = 65
Therefore, 16 * 63 = 65.
