PSLE Betty 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 190 days was $1036.40.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
(a)
Total number of coins
= 2 x 190
= 380
(b)
Number of sets of 2 days
= 190 ÷ 2
= 95
Amount that her mother put in
= 95 x 10
= $950
Amount that Betty saved by herself
= 1036.40 - 950
= $86.40
Number of 50¢ |
Value of 50¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
380 |
380 x 0.5 = 190 |
0 |
0 |
190 |
379 |
379 x 0.5 = 189.5 |
1 |
1 x 0.1 = 0.1 |
189.6 |
Small difference
= 190 - 189.6
= 0.4
Big difference
= 190 - 86.4
= 103.6
$1 = 100¢
$0.40 = 0.40 x 100 = 40¢
$103.60 = 103.60 x 100 = 10360¢
Number of 10¢ coins
= 10360 ÷ 40
= 259
Number of 50¢ coins
= 380 - 259
= 121
Answer(s): (a) 380; (b) 121