PSLE Jean started a savings plan by putting 2 coins into a money box every day. Each coin was either a 20¢ or 50¢ coin. Her father also put in $5 note in the box every 2 days. The total value of the savings after 186 days was $570.60.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 186
= 372
(b)
Number of sets of 2 days
= 186 ÷ 2
= 93
Amount that her father put in
= 93 x 5
= $465
Amount that Jean saved by herself
= 570.60 - 465
= $105.60
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
372 |
372 x 0.5 = 186 |
0 |
0 |
186 |
371 |
371 x 0.5 = 185.5 |
1 |
1 x 0.2 = 0.2 |
185.7 |
Small difference
= 186 - 185.7
= 0.3
Big difference
= 186 - 105.6
= 80.4
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$80.40 = 80.40 x 100 = 8040¢
Number of 20¢ coins
= 8040 ÷ 30
= 268
Number of 50¢ coins
= 372 - 268
= 104
Answer(s): (a) 372; (b) 104