A jar of pennies and nickles is worth 11.20 . There are three times as many pennies as nickles. How many pennies are in the jar?

Question

the possible answers are

a 260

b 420

c 580

d 640

Answer 1

Let p = the number of pennies and n = the number of nickels

• A jar of pennies and nickles is worth 11.20: ($0.01)p + ($0.05)n = $11.20
• There are three times as many pennies as nickles: p = 3n

 

The second equation tells us that p = 3n, so let's substitute 3n in place pf p in the first equation:

 

($0.01)p + ($0.05)n = $11.20

($0.01)(3n) + ($0.05)n = $11.20

0.03n + 0.05n = 11.2

0.08n = 11.2

n = 11.2/0.08

 

Solve for n, the number of nickels.  Once you have n, the number of pennies is p = 3n.