PSLE Marion started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 20¢ coin. Her uncle also put in $5 note in the box every 4 days. The total value of the savings after 152 days was $234.20.
- How many coins were there altogether?
- How many of the coins were 20¢ coins?
(a)
Total number of coins
= 2 x 152
= 304
(b)
Number of sets of 4 days
= 152 ÷ 4
= 38
Amount that her uncle put in
= 38 x 5
= $190
Amount that Marion saved by herself
= 234.20 - 190
= $44.20
Number of 20¢ |
Value of 20¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
304 |
304 x 0.2 = 60.8 |
0 |
0 |
60.8 |
303 |
303 x 0.2 = 60.6 |
1 |
1 x 0.1 = 0.1 |
60.7 |
Small difference
= 60.8 - 60.7
= 0.1
Big difference
= 60.8 - 44.2
= 16.6
$1 = 100¢
$0.10 = 0.10 x 100 = 10¢
$16.60 = 16.60 x 100 = 1660¢
Number of 10¢ coins
= 1660 ÷ 10
= 166
Number of 20¢ coins
= 304 - 166
= 138
Answer(s): (a) 304; (b) 138