The H.C.F of two 9/10,12/25,18/35 and 21/40 is:
$ \dfrac{3}{5} $
$ \dfrac{252}{5} $
$ \dfrac{3}{1400} $
$ \dfrac{63}{700} $
Explanation:
Required H.C.F. =$ \dfrac{H.C.F. of 9, 12, 18, 21}{L.C.M. of 10, 25, 35, 40} $=$ \dfrac{3}{1400} $