There are a total of 320 pieces of 5-cent coins, 10-cent coins and 20-cent coins in Carl's coin box.
35 of these coins are 5-cent coins. The number of 20-cent coins is thrice the number of 10-cent coins.
- How many 20-cent coins are there?
- What is the total value of the 20-cent coins in Carl's coin box?
(a)
Number of 5-cent coins
=
35 x 320
= 192
Number of 10-cent coins and 20-cent coins
= 320 - 192
= 128
Number of 10-cent coins = 1 u
Number of 20-cent coins = 3 u
Number of 10-cent coins
= 1 u + 3 u
= 4 u
4 u = 128
1 u = 128 ÷ 4 = 32
Number of 20-cent coins
= 3 u
= 3 x 32
= 96
(b)
100¢ = $1
Total value of the 20-cent coins in Carl's coin box
= 96 x 20
= 1920¢
= $19.20
Answer(s): (a) 96; (b) $19.20