If $m – n = 16$ and $m^2 + n^2 = 400$, the value of $mn$ is

72 25 144 192

72

Here, (m - n)2 = m2 + n2 - 2mn (16)2 = 400 – 2mn 256 = 400 – 2mn 256 – 400 = –2mn –144 = – 2mn 72 = mn So the value of mn =72