PSLE Min 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 $5 note in the box every 4 days. The total value of the savings after 116 days was $228.30.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 116
= 232
(b)
Number of sets of 4 days
= 116 ÷ 4
= 29
Amount that her father put in
= 29 x 5
= $145
Amount that Min saved by herself
= 228.30 - 145
= $83.30
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
232 |
232 x 0.5 = 116 |
0 |
0 |
116 |
231 |
231 x 0.5 = 115.5 |
1 |
1 x 0.2 = 0.2 |
115.7 |
Small difference
= 116 - 115.7
= 0.3
Big difference
= 116 - 83.3
= 32.7
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$32.70 = 32.70 x 100 = 3270¢
Number of 20¢ coins
= 3270 ÷ 30
= 109
Number of 50¢ coins
= 232 - 109
= 123
Answer(s): (a) 232; (b) 123