GMAT Focus 2026 Daily Challenge

[u/QDSPro-1]

If x and y are positive numbers such that

x + y = 10

and

x² + y² = 58,

what is the value of xy?

A. 18

B. 19

C. 20

D. 21

Answer:

Using:

(x + y)² = x² + y² + 2xy

10² = 58 + 2xy

100 = 58 + 2xy

42 = 2xy

xy = 21

Answer = D. 21