2\5 of the product of 5\6 and 42

Question

I do not know how to do this question and I have learned some of the way to do it and I was just hoping to get answers and my teacher has told us to use a certain method and I still can't seem to find the answer.

Answer 1

(2/5) [(5/6)(42)] = ?

 

Recall that 

 

42 = 6(7)

 

(2/5) [(5/6)(42)] = (2/5) [(5/6)(6)(7)] = (2 x 5 x 6 x 7) / (5 x 6)

 

Note both the numerator and denominator have a 5 and a 6, so you can cancel them, and get

 

(2/5) [(5/6)(42)] = 2 x 7 = 14