Bobby has 20-cent coins and 50-cent coins. The total value of all his coins is $35. He has 7 less 20-cent coins than 50-cent coins. How many coins does he have altogether?
|
20-cent |
50-cent |
Total |
Number |
1 u |
1 u + 7 |
2 u + 7 |
Value |
20 |
50 |
|
Total value |
20 u |
50 u + 350 |
70 u + 350 |
$1 = 100¢
$35 = 35 x 100 = 3500¢
Bobby has 7 more 50-cent coins than 20-cent coins.
Number of 20-cent coins = 1 u
Number of 50-cent coins = 1 u + 7
Total value of 20-cent coins
= 20 x 1 u
= 20 u
Total value of 50-cent coins
= 50 x (1 u + 7)
= 50 u + 350
Total value of the coins
= 20 u + 50 u + 350
= 70 u + 350
70 u + 350 = 3500
70 u = 3500 - 350
70 u = 3150
1 u = 3150 ÷ 70 = 45
Total number of coins
= 1 u + (1 u + 7)
= 2 u + 7
= 2 x 45 + 7
= 90 + 7
= 97
Answer(s): 97