Question

mary had twice as many 20 cent coins as 50 cent coins. if the coins added up to 13.50, how many 20 cent coins did mary have?

Answer 1

Answer:

Mary has 30, 20 cent coins

Step-by-step explanation:

Let the number of 20 cent coins and 50 cent coins be x and y respectively.

Given, 2y = x ---(1)

0.2x + 0.5y = 13.50 ---(2)

Substituting 1 in 2

0.2(2y) + 0.5y = 13.50

0.4y + 0.5y = 13.50

0.9y = 13.50

y = 15

x = 2 × 15 = 30