PSLE Lynn 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 $10 note in the box every 2 days. The total value of the savings after 158 days was $893.70.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 158
= 316
(b)
Number of sets of 2 days
= 158 ÷ 2
= 79
Amount that her father put in
= 79 x 10
= $790
Amount that Lynn saved by herself
= 893.70 - 790
= $103.70
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
316 |
316 x 0.5 = 158 |
0 |
0 |
158 |
315 |
315 x 0.5 = 157.5 |
1 |
1 x 0.2 = 0.2 |
157.7 |
Small difference
= 158 - 157.7
= 0.3
Big difference
= 158 - 103.7
= 54.3
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$54.30 = 54.30 x 100 = 5430¢
Number of 20¢ coins
= 5430 ÷ 30
= 181
Number of 50¢ coins
= 316 - 181
= 135
Answer(s): (a) 316; (b) 135