PSLE Lucy 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 $246.30.
- 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 Lucy saved by herself
= 246.30 - 126
= $120.30
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 - 120.3
= 68.7
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$68.70 = 68.70 x 100 = 6870¢
Number of 20¢ coins
= 6870 ÷ 30
= 229
Number of 50¢ coins
= 378 - 229
= 149
Answer(s): (a) 378; (b) 149