PSLE Betty 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 $2 note in the box every 2 days. The total value of the savings after 188 days was $235.90.
- How many coins were there altogether?
- How many of the coins were 20¢ coins?
(a)
Total number of coins
= 2 x 188
= 376
(b)
Number of sets of 2 days
= 188 ÷ 2
= 94
Amount that her uncle put in
= 94 x 2
= $188
Amount that Betty saved by herself
= 235.90 - 188
= $47.90
Number of 20¢ |
Value of 20¢ |
Number of 10¢ |
Value of 10¢ |
Total value |
376 |
376 x 0.2 = 75.2 |
0 |
0 |
75.2 |
375 |
375 x 0.2 = 75 |
1 |
1 x 0.1 = 0.1 |
75.1 |
Small difference
= 75.2 - 75.1
= 0.1
Big difference
= 75.2 - 47.9
= 27.3
$1 = 100¢
$0.10 = 0.10 x 100 = 10¢
$27.30 = 27.30 x 100 = 2730¢
Number of 10¢ coins
= 2730 ÷ 10
= 273
Number of 20¢ coins
= 376 - 273
= 103
Answer(s): (a) 376; (b) 103