PSLE Risa 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 $10 note in the box every 2 days. The total value of the savings after 132 days was $757.80.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 132
= 264
(b)
Number of sets of 2 days
= 132 ÷ 2
= 66
Amount that her uncle put in
= 66 x 10
= $660
Amount that Risa saved by herself
= 757.80 - 660
= $97.80
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
264 |
264 x 0.5 = 132 |
0 |
0 |
132 |
263 |
263 x 0.5 = 131.5 |
1 |
1 x 0.2 = 0.2 |
131.7 |
Small difference
= 132 - 131.7
= 0.3
Big difference
= 132 - 97.8
= 34.2
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$34.20 = 34.20 x 100 = 3420¢
Number of 20¢ coins
= 3420 ÷ 30
= 114
Number of 50¢ coins
= 264 - 114
= 150
Answer(s): (a) 264; (b) 150