There are a total of 390 pieces of 5-cent coins, 10-cent coins and 20-cent coins in Seth's piggy bank.
310 of these coins are 5-cent coins. The number of 20-cent coins is twice the number of 10-cent coins.
- How many 20-cent coins are there?
- What is the total value of the 20-cent coins in Seth's piggy bank?
(a)
Number of 5-cent coins
=
310 x 390
= 117
Number of 10-cent coins and 20-cent coins
= 390 - 117
= 273
Number of 10-cent coins = 1 u
Number of 20-cent coins = 2 u
Number of 10-cent coins
= 1 u + 2 u
= 3 u
3 u = 273
1 u = 273 ÷ 3 = 91
Number of 20-cent coins
= 2 u
= 2 x 91
= 182
(b)
100¢ = $1
Total value of the 20-cent coins in Seth's piggy bank
= 182 x 20
= 3640¢
= $36.40
Answer(s): (a) 182; (b) $36.40