PSLE Cathy 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 $2 note in the box every 3 days. The total value of the savings after 189 days was $237.60.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 189
= 378
(b)
Number of sets of 3 days
= 189 ÷ 3
= 63
Amount that her father put in
= 63 x 2
= $126
Amount that Cathy saved by herself
= 237.60 - 126
= $111.60
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
378 |
378 x 0.5 = 189 |
0 |
0 |
189 |
377 |
377 x 0.5 = 188.5 |
1 |
1 x 0.2 = 0.2 |
188.7 |
Small difference
= 189 - 188.7
= 0.3
Big difference
= 189 - 111.6
= 77.4
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$77.40 = 77.40 x 100 = 7740¢
Number of 20¢ coins
= 7740 ÷ 30
= 258
Number of 50¢ coins
= 378 - 258
= 120
Answer(s): (a) 378; (b) 120