PSLE Shannon 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 114 days was $157.90.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 114
= 228
(b)
Number of sets of 3 days
= 114 ÷ 3
= 38
Amount that her father put in
= 38 x 2
= $76
Amount that Shannon saved by herself
= 157.90 - 76
= $81.90
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
228 |
228 x 0.5 = 114 |
0 |
0 |
114 |
227 |
227 x 0.5 = 113.5 |
1 |
1 x 0.2 = 0.2 |
113.7 |
Small difference
= 114 - 113.7
= 0.3
Big difference
= 114 - 81.9
= 32.1
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$32.10 = 32.10 x 100 = 3210¢
Number of 20¢ coins
= 3210 ÷ 30
= 107
Number of 50¢ coins
= 228 - 107
= 121
Answer(s): (a) 228; (b) 121