Three number are in the ratio of 3 : 4 : 5 and their L.C.M. is 2400. Their H.C.F. is:
Let the numbers be 3$ x $, 4$ x $ and 5$ x $.
Then, their L.C.M. = 60$ x $.
So, 60$ x $ = 2400 or x = 40.
$\therefore$ The numbers are $\left(3 \times 40\right)$, $\left(4 \times 40\right)$ and $\left(5 \times 40\right)$.
Hence, required H.C.F. = 40.