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 $10 note in the box every 2 days. The total value of the savings after 176 days was $991.50.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 176
= 352
(b)
Number of sets of 2 days
= 176 ÷ 2
= 88
Amount that her father put in
= 88 x 10
= $880
Amount that Lucy saved by herself
= 991.50 - 880
= $111.50
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
352 |
352 x 0.5 = 176 |
0 |
0 |
176 |
351 |
351 x 0.5 = 175.5 |
1 |
1 x 0.2 = 0.2 |
175.7 |
Small difference
= 176 - 175.7
= 0.3
Big difference
= 176 - 111.5
= 64.5
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$64.50 = 64.50 x 100 = 6450¢
Number of 20¢ coins
= 6450 ÷ 30
= 215
Number of 50¢ coins
= 352 - 215
= 137
Answer(s): (a) 352; (b) 137