There are a total of 140 pieces of 5-cent coins, 10-cent coins and 20-cent coins in Tommy's piggy bank.
45 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 Tommy's piggy bank?
(a)
Number of 5-cent coins
=
45 x 140
= 112
Number of 10-cent coins and 20-cent coins
= 140 - 112
= 28
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 = 28
1 u = 28 ÷ 4 = 7
Number of 20-cent coins
= 3 u
= 3 x 7
= 21
(b)
100¢ = $1
Total value of the 20-cent coins in Tommy's piggy bank
= 21 x 20
= 420¢
= $4.20
Answer(s): (a) 21; (b) $4.20