PSLE Irene 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 $5 note in the box every 2 days. The total value of the savings after 172 days was $518.80.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 172
= 344
(b)
Number of sets of 2 days
= 172 ÷ 2
= 86
Amount that her father put in
= 86 x 5
= $430
Amount that Irene saved by herself
= 518.80 - 430
= $88.80
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
344 |
344 x 0.5 = 172 |
0 |
0 |
172 |
343 |
343 x 0.5 = 171.5 |
1 |
1 x 0.1 = 0.1 |
171.6 |
Small difference
= 172 - 171.6
= 0.4
Big difference
= 172 - 88.8
= 83.2
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$83.20 = 83.20 x 100 = 8320¢
Number of 10¢ coins
= 8320 ÷ 40
= 208
Number of 50¢ coins
= 344 - 208
= 136
Answer(s): (a) 344; (b) 136