The sum of the H.C.F. and L.C.M of two numbers is 680 and the LC.M. is 84 times the H.C.F. If one of the number is 56, the other is :

option 4 is the answer

Let HCF be h and
LCM be l.

Then, l = 84h and l + h= 680
84h + h = 680
h =$\frac{680}{85}$ =8

L = 680 – 8 = 672
Other number

$\frac{672\times8}{56}$ = 56