Ahmad has 10-cent coins and 20-cent coins. The total value of all his coins is $26. He has 13 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 + 13 |
2 u + 13 |
| Value |
10 |
20 |
|
| Total value |
10 u |
20 u + 260 |
30 u + 260 |
$1 = 100¢
$26 = 26 x 100 = 2600¢
Ahmad has 13 more 20-cent coins than 10-cent coins.
Number of 10-cent coins = 1 u
Number of 20-cent coins = 1 u + 13
Total value of 10-cent coins
= 10 x 1 u
= 10 u
Total value of 20-cent coins
= 20 x (1 u + 13)
= 20 u + 260
Total value of the coins
= 10 u + 20 u + 260
= 30 u + 260
30 u + 260 = 2600
30 u = 2600 - 260
30 u = 2340
1 u = 2340 ÷ 30 = 78
Total number of coins
= 1 u + (1 u + 13)
= 2 u + 13
= 2 x 78 + 13
= 156 + 13
= 169
Answer(s): 169
