PSLE Kimberly 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 3 days. The total value of the savings after 147 days was $559.40.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 147
= 294
(b)
Number of sets of 3 days
= 147 ÷ 3
= 49
Amount that her aunt put in
= 49 x 10
= $490
Amount that Kimberly saved by herself
= 559.40 - 490
= $69.40
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
294 |
294 x 0.5 = 147 |
0 |
0 |
147 |
293 |
293 x 0.5 = 146.5 |
1 |
1 x 0.1 = 0.1 |
146.6 |
Small difference
= 147 - 146.6
= 0.4
Big difference
= 147 - 69.4
= 77.6
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$77.60 = 77.60 x 100 = 7760¢
Number of 10¢ coins
= 7760 ÷ 40
= 194
Number of 50¢ coins
= 294 - 194
= 100
Answer(s): (a) 294; (b) 100