PSLE Jaslyn started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 20¢ coin. Her aunt also put in $2 note in the box every 2 days. The total value of the savings after 130 days was $169.60.
- How many coins were there altogether?
- How many of the coins were 20¢ coins?
(a)
Total number of coins
= 2 x 130
= 260
(b)
Number of sets of 2 days
= 130 ÷ 2
= 65
Amount that her aunt put in
= 65 x 2
= $130
Amount that Jaslyn saved by herself
= 169.60 - 130
= $39.60
Number of 20¢ |
Value of 20¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
260 |
260 x 0.2 = 52 |
0 |
0 |
52 |
259 |
259 x 0.2 = 51.8 |
1 |
1 x 0.1 = 0.1 |
51.9 |
Small difference
= 52 - 51.9
= 0.1
Big difference
= 52 - 39.6
= 12.4
$1 = 100¢
$0.10 = 0.10 x 100 = 10¢
$12.40 = 12.40 x 100 = 1240¢
Number of 10¢ coins
= 1240 ÷ 10
= 124
Number of 20¢ coins
= 260 - 124
= 136
Answer(s): (a) 260; (b) 136