PSLE Linda started a savings plan by putting 2 coins into a money box every day. Each coin was either a 20¢ or 50¢ coin. Her mother also put in $5 note in the box every 4 days. The total value of the savings after 112 days was $219.90.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 112
= 224
(b)
Number of sets of 4 days
= 112 ÷ 4
= 28
Amount that her mother put in
= 28 x 5
= $140
Amount that Linda saved by herself
= 219.90 - 140
= $79.90
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
224 |
224 x 0.5 = 112 |
0 |
0 |
112 |
223 |
223 x 0.5 = 111.5 |
1 |
1 x 0.2 = 0.2 |
111.7 |
Small difference
= 112 - 111.7
= 0.3
Big difference
= 112 - 79.9
= 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
= 224 - 107
= 117
Answer(s): (a) 224; (b) 117