PSLE Wendy 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 4 days. The total value of the savings after 172 days was $533.30.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 172
= 344
(b)
Number of sets of 4 days
= 172 ÷ 4
= 43
Amount that her father put in
= 43 x 10
= $430
Amount that Wendy saved by herself
= 533.30 - 430
= $103.30
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
344 |
344 x 0.5 = 172 |
0 |
0 |
172 |
343 |
343 x 0.5 = 171.5 |
1 |
1 x 0.2 = 0.2 |
171.7 |
Small difference
= 172 - 171.7
= 0.3
Big difference
= 172 - 103.3
= 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
= 344 - 229
= 115
Answer(s): (a) 344; (b) 115