A Real Life Example of Multiplication of Fractions

by Kellie B
(Ann Arbor, MI)

Johnny works at a local bakery. In the morning Customer #1 buys 1/2 a pan of brownies. Later, Customer #2 buys 1/4 of the remaining brownies. The brownies cost $10 for a whole tray.

How much did Customer #1 pay for his brownies? ___________



What fraction of a pan did Customer #2 buy? _______________



How much did Customer #2 pay for his brownies? ___________



Solution


Customer #1

Customer #1 bought half or 1/2 of the whole tray.

The tray cost 10. Half of 10 is 5

Another way to do the computation is to do

1/2 × 10 = (1 × 10) / 2 = 10 / 2 = 5

Customer #1 paid 5 dollars for his brownies

Customer #2

Customer 2 bought 1/4 of the remaining brownies.


The remaining brownies is 1/2

Thus, customer #2 bought 1/4 of 1/2

1/4 of 1/2 = 1/4 × 1/2

= (1 × 1) / (4 × 2)

= 1 / 8

Customer #2 bought 1/8 of the brownies

The fraction of a pan Customer #2 bought is 1/8

Customer #2 only bought 1/8 of the brownies.

So just find out what 1/8 of 10 is

1/8 of 10 = 1/8 × 10

1/8 × 10 = ( 1 × 10 ) / 8 = 10 / 8 = 1.25

Customer #2 paid 1.25 dollar for his brownies?