PSLE Dana started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 50¢ coin. Her mother also put in $10 note in the box every 2 days. The total value of the savings after 178 days was $982.80.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 178
= 356
(b)
Number of sets of 2 days
= 178 ÷ 2
= 89
Amount that her mother put in
= 89 x 10
= $890
Amount that Dana saved by herself
= 982.80 - 890
= $92.80
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
356 |
356 x 0.5 = 178 |
0 |
0 |
178 |
355 |
355 x 0.5 = 177.5 |
1 |
1 x 0.1 = 0.1 |
177.6 |
Small difference
= 178 - 177.6
= 0.4
Big difference
= 178 - 92.8
= 85.2
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$85.20 = 85.20 x 100 = 8520¢
Number of 10¢ coins
= 8520 ÷ 40
= 213
Number of 50¢ coins
= 356 - 213
= 143
Answer(s): (a) 356; (b) 143