Ian has 10-cent coins and 20-cent coins. The total value of all his coins is $25. He has 17 less 10-cent coins than 20-cent coins. How many coins does he have altogether?
|
10-cent |
20-cent |
Total |
Number |
1 u |
1 u + 17 |
2 u + 17 |
Value |
10 |
20 |
|
Total value |
10 u |
20 u + 340 |
30 u + 340 |
$1 = 100¢
$25 = 25 x 100 = 2500¢
Ian has 17 more 20-cent coins than 10-cent coins.
Number of 10-cent coins = 1 u
Number of 20-cent coins = 1 u + 17
Total value of 10-cent coins
= 10 x 1 u
= 10 u
Total value of 20-cent coins
= 20 x (1 u + 17)
= 20 u + 340
Total value of the coins
= 10 u + 20 u + 340
= 30 u + 340
30 u + 340 = 2500
30 u = 2500 - 340
30 u = 2160
1 u = 2160 ÷ 30 = 72
Total number of coins
= 1 u + (1 u + 17)
= 2 u + 17
= 2 x 72 + 17
= 144 + 17
= 161
Answer(s): 161