There are a total of 180 pieces of 5-cent coins, 10-cent coins and 20-cent coins in David's piggy bank.
23 of these coins are 5-cent coins. The number of 20-cent coins is four times the number of 10-cent coins.
- How many 20-cent coins are there?
- What is the total value of the 20-cent coins in David's piggy bank?
(a)
Number of 5-cent coins
=
23 x 180
= 120
Number of 10-cent coins and 20-cent coins
= 180 - 120
= 60
Number of 10-cent coins = 1 u
Number of 20-cent coins = 4 u
Number of 10-cent coins
= 1 u + 4 u
= 5 u
5 u = 60
1 u = 60 ÷ 5 = 12
Number of 20-cent coins
= 4 u
= 4 x 12
= 48
(b)
100¢ = $1
Total value of the 20-cent coins in David's piggy bank
= 48 x 20
= 960¢
= $9.60
Answer(s): (a) 48; (b) $9.60