PSLE Hilda 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 3 days. The total value of the savings after 147 days was $328.80.
- 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 mother put in
= 49 x 5
= $245
Amount that Hilda saved by herself
= 328.80 - 245
= $83.80
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 - 83.8
= 63.2
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$63.20 = 63.20 x 100 = 6320¢
Number of 10¢ coins
= 6320 ÷ 40
= 158
Number of 50¢ coins
= 294 - 158
= 136
Answer(s): (a) 294; (b) 136