find the HCF of 9/10, 12/25, 18/35, 21/40

pls answer fast

We know that, 

Prime factorization of

9 = 3 × 3

12 = 2 × 2 × 3

18 = 2 × 3 × 3

21 = 3 × 7

HCF of 9, 12, 18 and 21 = 3

Prime factorization of

10 = 2 × 5

25 = 5 × 5

35 = 5 × 7

40 = 2 × 2 × 2 × 5

LCM of 10, 25, 35 and 40 = 2 × 2 × 2 × 5 × 5 × 7 = 1400

                     [Using (1)]