Howard has 10-cent coins and 20-cent coins. The total value of all his coins is $29. He has 10 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 + 10 |
2 u + 10 |
Value |
10 |
20 |
|
Total value |
10 u |
20 u + 200 |
30 u + 200 |
$1 = 100¢
$29 = 29 x 100 = 2900¢
Howard has 10 more 20-cent coins than 10-cent coins.
Number of 10-cent coins = 1 u
Number of 20-cent coins = 1 u + 10
Total value of 10-cent coins
= 10 x 1 u
= 10 u
Total value of 20-cent coins
= 20 x (1 u + 10)
= 20 u + 200
Total value of the coins
= 10 u + 20 u + 200
= 30 u + 200
30 u + 200 = 2900
30 u = 2900 - 200
30 u = 2700
1 u = 2700 ÷ 30 = 90
Total number of coins
= 1 u + (1 u + 10)
= 2 u + 10
= 2 x 90 + 10
= 180 + 10
= 190
Answer(s): 190