PSLE Zara started a savings plan by putting 2 coins into a money box every day. Each coin was either a 20¢ or 50¢ coin. Her uncle also put in $2 note in the box every 5 days. The total value of the savings after 175 days was $177.20.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 175
= 350
(b)
Number of sets of 5 days
= 175 ÷ 5
= 35
Amount that her uncle put in
= 35 x 2
= $70
Amount that Zara saved by herself
= 177.20 - 70
= $107.20
Number of 50¢ |
Value of 50¢ |
Number of 20¢ |
Value of 20¢ |
Total value |
350 |
350 x 0.5 = 175 |
0 |
0 |
175 |
349 |
349 x 0.5 = 174.5 |
1 |
1 x 0.2 = 0.2 |
174.7 |
Small difference
= 175 - 174.7
= 0.3
Big difference
= 175 - 107.2
= 67.8
$1 = 100¢
$0.30 = 0.30 x 100 = 30¢
$67.80 = 67.80 x 100 = 6780¢
Number of 20¢ coins
= 6780 ÷ 30
= 226
Number of 50¢ coins
= 350 - 226
= 124
Answer(s): (a) 350; (b) 124