PSLE Sarah started a savings plan by putting 2 coins into a money box every day. Each coin was either a 20¢ or 50¢ coin. Her father also put in $10 note in the box every 2 days. The total value of the savings after 146 days was $826.80.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 146
= 292
(b)
Number of sets of 2 days
= 146 ÷ 2
= 73
Amount that her father put in
= 73 x 10
= $730
Amount that Sarah saved by herself
= 826.80 - 730
= $96.80
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
292 |
292 x 0.5 = 146 |
0 |
0 |
146 |
291 |
291 x 0.5 = 145.5 |
1 |
1 x 0.2 = 0.2 |
145.7 |
Small difference
= 146 - 145.7
= 0.3
Big difference
= 146 - 96.8
= 49.2
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$49.20 = 49.20 x 100 = 4920¢
Number of 20¢ coins
= 4920 ÷ 30
= 164
Number of 50¢ coins
= 292 - 164
= 128
Answer(s): (a) 292; (b) 128