PSLE Raeann started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 50¢ coin. Her mother also put in $2 note in the box every 2 days. The total value of the savings after 162 days was $242.40.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 162
= 324
(b)
Number of sets of 2 days
= 162 ÷ 2
= 81
Amount that her mother put in
= 81 x 2
= $162
Amount that Raeann saved by herself
= 242.40 - 162
= $80.40
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
324 |
324 x 0.5 = 162 |
0 |
0 |
162 |
323 |
323 x 0.5 = 161.5 |
1 |
1 x 0.1 = 0.1 |
161.6 |
Small difference
= 162 - 161.6
= 0.4
Big difference
= 162 - 80.4
= 81.6
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$81.60 = 81.60 x 100 = 8160¢
Number of 10¢ coins
= 8160 ÷ 40
= 204
Number of 50¢ coins
= 324 - 204
= 120
Answer(s): (a) 324; (b) 120