Eric started saving part of his pocket money by putting 2 coins in a money box every day. Each coin was either a 20¢ or 50¢ coin. His father also put on a $1 coin in the box every 7 days. The total value of the coins after 91 days was $66.20.
- How many coins were there altogether?
- How many of the coins were 50¢ coins?
Total nuber of coins that his father put in
= 91 ÷ 7
= 13
Total number of coins that Eric saved
= 2 x 91 = 182 Total number of coins
= 13 + 182
= 195
(b)
Amount contributed by his father
= 13 x 1
= $13
Amount that Eric saved
= 66.20 - 13
= $53.20
$1 = 100¢
$53.20 = 5320¢
Number of
50¢ coins |
Total value
of 50¢ coins |
Number of
20¢ coins |
Total value
of 20¢ coins |
Total value |
182
|
182 x 50
= 9100¢ |
0
|
0
|
9100¢
|
181
|
181 x 50
= 9050¢ |
1
|
1 x 20 =
20¢ |
9070¢
|
| 56 |
56 x 50
= 2800¢ |
126 |
126 x 20 =
2520¢ |
5320¢
|
Amount that Eric saved if all he saved were 50¢ coins
= 182 x 50
= 9100
Big difference between the total values of 50¢ coins and 20¢ coins
= 9100 - 5320
= 3780
Small difference between the value of 50¢ coins and 20¢ coins
= 50 - 20
= 30
Number of 20¢ coins
= 3780 ÷ 30
= 126
Number of 50¢ coins
= 182 - 126
= 56
Answer(s): (a) 195; (b) 56
