PSLE Tammy started a savings plan by putting 2 coins into a money box every day. Each coin was either a 10¢ or 50¢ coin. Her mother also put in $2 note in the box every 5 days. The total value of the savings after 175 days was $160.20.
- 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 mother put in
= 35 x 2
= $70
Amount that Tammy saved by herself
= 160.20 - 70
= $90.20
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
350 |
350 x 0.5 = 175 |
0 |
0 |
175 |
349 |
349 x 0.5 = 174.5 |
1 |
1 x 0.1 = 0.1 |
174.6 |
Small difference
= 175 - 174.6
= 0.4
Big difference
= 175 - 90.2
= 84.8
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$84.80 = 84.80 x 100 = 8480¢
Number of 10¢ coins
= 8480 ÷ 40
= 212
Number of 50¢ coins
= 350 - 212
= 138
Answer(s): (a) 350; (b) 138