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 uncle also put in $5 note in the box every 2 days. The total value of the savings after 142 days was $449.60.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 142
= 284
(b)
Number of sets of 2 days
= 142 ÷ 2
= 71
Amount that her uncle put in
= 71 x 5
= $355
Amount that Sarah saved by herself
= 449.60 - 355
= $94.60
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
284 |
284 x 0.5 = 142 |
0 |
0 |
142 |
283 |
283 x 0.5 = 141.5 |
1 |
1 x 0.2 = 0.2 |
141.7 |
Small difference
= 142 - 141.7
= 0.3
Big difference
= 142 - 94.6
= 47.4
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$47.40 = 47.40 x 100 = 4740¢
Number of 20¢ coins
= 4740 ÷ 30
= 158
Number of 50¢ coins
= 284 - 158
= 126
Answer(s): (a) 284; (b) 126