Question

Use a method of your own choice to find the H.C.F. of 30, 60, 90 and 105.

Answer 1

Factor of 30 = F₃₀ = 2 x 3 x 5
Factor of 60 = F₆₀ = 2 x 2 x 3 x 5
Factor of 90 = F₉₀ = 2 x 3 x 3 x 5
and factor of 105 = F₁₀₅ = 3 x 5 x 7
Now the common factor of 30, 60, 90 and 105 = 3 and 5
H.C.F. = 3 x 5 = 15