PSLE Sabrina started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 50¢ coin. Her mother also put in $5 note in the box every 2 days. The total value of the savings after 186 days was $544.20.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 186
= 372
(b)
Number of sets of 2 days
= 186 ÷ 2
= 93
Amount that her mother put in
= 93 x 5
= $465
Amount that Sabrina saved by herself
= 544.20 - 465
= $79.20
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
372 |
372 x 0.5 = 186 |
0 |
0 |
186 |
371 |
371 x 0.5 = 185.5 |
1 |
1 x 0.1 = 0.1 |
185.6 |
Small difference
= 186 - 185.6
= 0.4
Big difference
= 186 - 79.2
= 106.8
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$106.80 = 106.80 x 100 = 10680¢
Number of 10¢ coins
= 10680 ÷ 40
= 267
Number of 50¢ coins
= 372 - 267
= 105
Answer(s): (a) 372; (b) 105