PSLE Zara started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 50¢ coin. Her aunt also put in $5 note in the box every 2 days. The total value of the savings after 138 days was $416.20.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 138
= 276
(b)
Number of sets of 2 days
= 138 ÷ 2
= 69
Amount that her aunt put in
= 69 x 5
= $345
Amount that Zara saved by herself
= 416.20 - 345
= $71.20
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
276 |
276 x 0.5 = 138 |
0 |
0 |
138 |
275 |
275 x 0.5 = 137.5 |
1 |
1 x 0.1 = 0.1 |
137.6 |
Small difference
= 138 - 137.6
= 0.4
Big difference
= 138 - 71.2
= 66.8
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$66.80 = 66.80 x 100 = 6680¢
Number of 10¢ coins
= 6680 ÷ 40
= 167
Number of 50¢ coins
= 276 - 167
= 109
Answer(s): (a) 276; (b) 109