Cole started saving part of his pocket money by putting 2 coins in a money box every day. Each coin was either a 10¢ or 20¢ coin. His grandfather also put on a $1 coin in the box every 7 days. The total value of the coins after 49 days was $25.80.
- How many coins were there altogether?
- How many of the coins were 20¢ coins?
Total nuber of coins that his grandfather put in
= 49 ÷ 7
= 7
Total number of coins that Cole saved
= 2 x 49 = 98 Total number of coins
= 7 + 98
= 105
(b)
Amount contributed by his grandfather
= 7 x 1
= $7
Amount that Cole saved
= 25.80 - 7
= $18.80
$1 = 100¢
$18.80 = 1880¢
Number of 20¢ coins |
Total value of 20¢ coins |
Number of 10¢ coins |
Total value of 10¢ coins |
Total value |
98
|
98 x 20 = 1960¢ |
0
|
0
|
1960¢
|
97
|
97 x 20 = 1940¢ |
1
|
1 x 10 = 10¢ |
1950¢
|
90 |
90 x 20 = 1800¢ |
8 |
8 x 10 = 80¢ |
1880¢
|
Amount that Cole saved if all he saved were 20¢ coins
= 98 x 20
= 1960
Big difference between the total values of 20¢ coins and 10¢ coins
= 1960 - 1880
= 80
Small difference between the value of 20¢ coins and 10¢ coins
= 20 - 10
= 10
Number of 10¢ coins
= 80 ÷ 10
= 8
Number of 20¢ coins
= 98 - 8
= 90
Answer(s): (a) 105; (b) 90