PSLE Gillian started a savings plan by putting 2 coins into a money box every day. Each coin was either a 20¢ or 50¢ coin. Her uncle also put in $2 note in the box every 2 days. The total value of the savings after 106 days was $189.80.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 106
= 212
(b)
Number of sets of 2 days
= 106 ÷ 2
= 53
Amount that her uncle put in
= 53 x 2
= $106
Amount that Gillian saved by herself
= 189.80 - 106
= $83.80
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
212 |
212 x 0.5 = 106 |
0 |
0 |
106 |
211 |
211 x 0.5 = 105.5 |
1 |
1 x 0.2 = 0.2 |
105.7 |
Small difference
= 106 - 105.7
= 0.3
Big difference
= 106 - 83.8
= 22.2
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$22.20 = 22.20 x 100 = 2220¢
Number of 20¢ coins
= 2220 ÷ 30
= 74
Number of 50¢ coins
= 212 - 74
= 138
Answer(s): (a) 212; (b) 138