The product of two numbers is 1600 and their HCF is 5. The LCM of the numbers is

(c) 320
Let the two numbers be x and y.
It is given that:

$x \times y=1600$

HCF = 5

We know,

$\mathrm{HCF} \times \mathrm{LCM}=x \times y$

$\Rightarrow \quad 5 \times \mathrm{LCM}=1600$

$\Rightarrow \quad \therefore \angle C M=\frac{1600}{5}=320$