PSLE Abi started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 50¢ coin. Her father also put in $10 note in the box every 4 days. The total value of the savings after 144 days was $433.60.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 144
= 288
(b)
Number of sets of 4 days
= 144 ÷ 4
= 36
Amount that her father put in
= 36 x 10
= $360
Amount that Abi saved by herself
= 433.60 - 360
= $73.60
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
288 |
288 x 0.5 = 144 |
0 |
0 |
144 |
287 |
287 x 0.5 = 143.5 |
1 |
1 x 0.1 = 0.1 |
143.6 |
Small difference
= 144 - 143.6
= 0.4
Big difference
= 144 - 73.6
= 70.4
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$70.40 = 70.40 x 100 = 7040¢
Number of 10¢ coins
= 7040 ÷ 40
= 176
Number of 50¢ coins
= 288 - 176
= 112
Answer(s): (a) 288; (b) 112