If the ratio of two numbers is $5:7$ and their H.C.F. is $4$, the L.C.M. of the numbers is—

With ratio $5:7$ and H.C.F. $4$, the numbers are $5\times4=20$ and $7\times4=28$. The L.C.M. equals the product of the ratio terms and the H.C.F.: $5\times7\times4=140$.