PSLE Nicole 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 100 days was $110.40.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 100
= 200
(b)
Number of sets of 4 days
= 100 ÷ 4
= 25
Amount that her father put in
= 25 x 2
= $50
Amount that Nicole saved by herself
= 110.40 - 50
= $60.40
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
200 |
200 x 0.5 = 100 |
0 |
0 |
100 |
199 |
199 x 0.5 = 99.5 |
1 |
1 x 0.1 = 0.1 |
99.6 |
Small difference
= 100 - 99.6
= 0.4
Big difference
= 100 - 60.4
= 39.6
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$39.60 = 39.60 x 100 = 3960¢
Number of 10¢ coins
= 3960 ÷ 40
= 99
Number of 50¢ coins
= 200 - 99
= 101
Answer(s): (a) 200; (b) 101