Tommy has 5-cent coins and 10-cent coins. The total value of all his coins is $11. He has 5 less 5-cent coins than 10-cent coins. How many coins does he have altogether?
| |
5-cent |
10-cent |
Total |
| Number |
1 u |
1 u + 5 |
2 u + 5 |
| Value |
5 |
10 |
|
| Total value |
5 u |
10 u + 50 |
15 u + 50 |
$1 = 100¢
$11 = 11 x 100 = 1100¢
Tommy has 5 more 10-cent coins than 5-cent coins.
Number of 5-cent coins = 1 u
Number of 10-cent coins = 1 u + 5
Total value of 5-cent coins
= 5 x 1 u
= 5 u
Total value of 10-cent coins
= 10 x (1 u + 5)
= 10 u + 50
Total value of the coins
= 5 u + 10 u + 50
= 15 u + 50
15 u + 50 = 1100
15 u = 1100 - 50
15 u = 1050
1 u = 1050 ÷ 15 = 70
Total number of coins
= 1 u + (1 u + 5)
= 2 u + 5
= 2 x 70 + 5
= 140 + 5
= 145
Answer(s): 145
