Simon started saving part of his pocket money by putting 2 coins in a money box every day. Each coin was either a 10¢ or 50¢ coin. His mother also put on a $1 coin in the box every 7 days. The total value of the coins after 63 days was $54.80.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
Total nuber of coins that his mother put in
= 63 ÷ 7
= 9
Total number of coins that Simon saved
= 2 x 63 = 126 Total number of coins
= 9 + 126
= 135
(b)
Amount contributed by his mother
= 9 x 1
= $9
Amount that Simon saved
= 54.80 - 9
= $45.80
$1 = 100¢
$45.80 = 4580¢
Number of 50¢ coins |
Total value of 50¢ coins |
Number of 10¢ coins |
Total value of 10¢ coins |
Total value |
126
|
126 x 50 = 6300¢ |
0
|
0
|
6300¢
|
125
|
125 x 50 = 6250¢ |
1
|
1 x 10 = 10¢ |
6260¢
|
83 |
83 x 50 = 4150¢ |
43 |
43 x 10 = 430¢ |
4580¢
|
Amount that Simon saved if all he saved were 50¢ coins
= 126 x 50
= 6300
Big difference between the total values of 50¢ coins and 10¢ coins
= 6300 - 4580
= 1720
Small difference between the value of 50¢ coins and 10¢ coins
= 50 - 10
= 40
Number of 10¢ coins
= 1720 ÷ 40
= 43
Number of 50¢ coins
= 126 - 43
= 83
Answer(s): (a) 135; (b) 83