Justin has 5-cent coins and 10-cent coins. The total value of all his coins is $18. He has 18 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 + 18 |
2 u + 18 |
Value |
5 |
10 |
|
Total value |
5 u |
10 u + 180 |
15 u + 180 |
$1 = 100¢
$18 = 18 x 100 = 1800¢
Justin has 18 more 10-cent coins than 5-cent coins.
Number of 5-cent coins = 1 u
Number of 10-cent coins = 1 u + 18
Total value of 5-cent coins
= 5 x 1 u
= 5 u
Total value of 10-cent coins
= 10 x (1 u + 18)
= 10 u + 180
Total value of the coins
= 5 u + 10 u + 180
= 15 u + 180
15 u + 180 = 1800
15 u = 1800 - 180
15 u = 1620
1 u = 1620 ÷ 15 = 108
Total number of coins
= 1 u + (1 u + 18)
= 2 u + 18
= 2 x 108 + 18
= 216 + 18
= 234
Answer(s): 234