Question

Russell has a collection of 1,200 pennies. Of these pennies, 25% are dated before 1980, 35% are dated from 1980 to 2000, and the rest are dated after 2000. How many pennies in Russell’s collection are dated after 2000?

Answer 1

Answer:

480 pennies dated after 2000.

Step-by-step explanation:

1. Pennies dated before 1980 (x) - 25%,

All pennies (1,200) - 100%.

Then

$\dfrac{x}{1,200}=\dfrac{25}{100},\\ \\100x=25\cdot 1,200,\\ \\x=25\cdot 12=300.$

2. Pennies dated from 1980 to 2000 (y) - 35%,

All pennies (1,200) - 100%.

Then

$\dfrac{y}{1,200}=\dfrac{35}{100},\\ \\100y=35\cdot 1,200,\\ \\y=35\cdot 12=420.$

3. Rest pennies are dated after 2000, then

$1,200-300-420=480.$