Sam has 10-cent coins and 20-cent coins. The total value of all his coins is $11. He has 16 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 + 16 |
2 u + 16 |
Value |
10 |
20 |
|
Total value |
10 u |
20 u + 320 |
30 u + 320 |
$1 = 100¢
$11 = 11 x 100 = 1100¢
Sam has 16 more 20-cent coins than 10-cent coins.
Number of 10-cent coins = 1 u
Number of 20-cent coins = 1 u + 16
Total value of 10-cent coins
= 10 x 1 u
= 10 u
Total value of 20-cent coins
= 20 x (1 u + 16)
= 20 u + 320
Total value of the coins
= 10 u + 20 u + 320
= 30 u + 320
30 u + 320 = 1100
30 u = 1100 - 320
30 u = 780
1 u = 780 ÷ 30 = 26
Total number of coins
= 1 u + (1 u + 16)
= 2 u + 16
= 2 x 26 + 16
= 52 + 16
= 68
Answer(s): 68