RRB NTPC 18 January 2017 Paper

(2) Let the numbers be x and y.
According to the question,
x + y = 42
x – y = 4
On adding both equations,
2x = 46
⇒ x = 23
Putting x = 23 in x + y = 42
23 + y = 421
y = 19
Then x y = 23 × 19 = 437