Question

The cost of 8 pens is $2. 50. How much will 2 dozen cost?.

Answer 1

$ 7.5

Step-by-step explanation:

1. Common way:

if one pen costs $ x

8x=2.5

x=0.3125

2 dozen = 24

24*0.3125=7.5

2. shortcut:

2 dozen = 24 = 3 times of 8

because 8 pens cost $2.5, 2 dozen pens cost 3 times of $2.5, thus, $7.5