PSLE Linda started a savings plan by putting 2 coins into a money box every day. Each coin was either a 20¢ or 50¢ coin. Her aunt also put in $5 note in the box every 2 days. The total value of the savings after 140 days was $444.40.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 140
= 280
(b)
Number of sets of 2 days
= 140 ÷ 2
= 70
Amount that her aunt put in
= 70 x 5
= $350
Amount that Linda saved by herself
= 444.40 - 350
= $94.40
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
280 |
280 x 0.5 = 140 |
0 |
0 |
140 |
279 |
279 x 0.5 = 139.5 |
1 |
1 x 0.2 = 0.2 |
139.7 |
Small difference
= 140 - 139.7
= 0.3
Big difference
= 140 - 94.4
= 45.6
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$45.60 = 45.60 x 100 = 4560¢
Number of 20¢ coins
= 4560 ÷ 30
= 152
Number of 50¢ coins
= 280 - 152
= 128
Answer(s): (a) 280; (b) 128