PSLE Diana started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 50¢ coin. Her aunt also put in $10 note in the box every 4 days. The total value of the savings after 196 days was $589.20.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 196
= 392
(b)
Number of sets of 4 days
= 196 ÷ 4
= 49
Amount that her aunt put in
= 49 x 10
= $490
Amount that Diana saved by herself
= 589.20 - 490
= $99.20
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
392 |
392 x 0.5 = 196 |
0 |
0 |
196 |
391 |
391 x 0.5 = 195.5 |
1 |
1 x 0.1 = 0.1 |
195.6 |
Small difference
= 196 - 195.6
= 0.4
Big difference
= 196 - 99.2
= 96.8
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$96.80 = 96.80 x 100 = 9680¢
Number of 10¢ coins
= 9680 ÷ 40
= 242
Number of 50¢ coins
= 392 - 242
= 150
Answer(s): (a) 392; (b) 150