PSLE Yen started a savings plan by putting 2 coins into a money box every day. Each coin was either a 20¢ or 50¢ coin. Her uncle also put in $10 note in the box every 2 days. The total value of the savings after 154 days was $869.40.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 154
= 308
(b)
Number of sets of 2 days
= 154 ÷ 2
= 77
Amount that her uncle put in
= 77 x 10
= $770
Amount that Yen saved by herself
= 869.40 - 770
= $99.40
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
308 |
308 x 0.5 = 154 |
0 |
0 |
154 |
307 |
307 x 0.5 = 153.5 |
1 |
1 x 0.2 = 0.2 |
153.7 |
Small difference
= 154 - 153.7
= 0.3
Big difference
= 154 - 99.4
= 54.6
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$54.60 = 54.60 x 100 = 5460¢
Number of 20¢ coins
= 5460 ÷ 30
= 182
Number of 50¢ coins
= 308 - 182
= 126
Answer(s): (a) 308; (b) 126