Question

A pile of 20 sheets of card is 1cm high,how high is a pile of 50 sheets of card?

Answer 1

1/20 = .05
so each sheet is .05 of a cm.
50*.05 = 2.5
by multiplying 50 (the number of sheet) by .05 (the height of one card) you get 2.5 the height of 50 cards.

Answer 2

20 / 1 = 50 / x.....20 sheets to 1 cm = 50 sheets to x cm
cross multiply
(20)(x) = (1)(50)
20x = 50
x = 50/20
x = 5/2 = 2 1/2 cm (or 2.5 cm) <==