PSLE Cathy 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 $2 note in the box every 4 days. The total value of the savings after 124 days was $136.80.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 124
= 248
(b)
Number of sets of 4 days
= 124 ÷ 4
= 31
Amount that her father put in
= 31 x 2
= $62
Amount that Cathy saved by herself
= 136.80 - 62
= $74.80
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
248 |
248 x 0.5 = 124 |
0 |
0 |
124 |
247 |
247 x 0.5 = 123.5 |
1 |
1 x 0.1 = 0.1 |
123.6 |
Small difference
= 124 - 123.6
= 0.4
Big difference
= 124 - 74.8
= 49.2
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$49.20 = 49.20 x 100 = 4920¢
Number of 10¢ coins
= 4920 ÷ 40
= 123
Number of 50¢ coins
= 248 - 123
= 125
Answer(s): (a) 248; (b) 125