PSLE Tiffany 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 $10 note in the box every 2 days. The total value of the savings after 154 days was $851.20.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 154
= 308
(b)
Number of sets of 2 days
= 154 ÷ 2
= 77
Amount that her mother put in
= 77 x 10
= $770
Amount that Tiffany saved by herself
= 851.20 - 770
= $81.20
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
308 |
308 x 0.5 = 154 |
0 |
0 |
154 |
307 |
307 x 0.5 = 153.5 |
1 |
1 x 0.1 = 0.1 |
153.6 |
Small difference
= 154 - 153.6
= 0.4
Big difference
= 154 - 81.2
= 72.8
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$72.80 = 72.80 x 100 = 7280¢
Number of 10¢ coins
= 7280 ÷ 40
= 182
Number of 50¢ coins
= 308 - 182
= 126
Answer(s): (a) 308; (b) 126