SOLUTION: In my purse I have 21 coins, all of which are either 5-cent or 20-cent coins. Their total value is $2.25.
How many 20-cent coins do I have?
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How many 20-cent coins do I have?
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Question 1046262: In my purse I have 21 coins, all of which are either 5-cent or 20-cent coins. Their total value is $2.25.
How many 20-cent coins do I have? Answer by ikleyn(52778) (Show Source):
You can put this solution on YOUR website! .
In my purse I have 21 coins, all of which are either 5-cent or 20-cent coins. Their total value is $2.25.
How many 20-cent coins do I have?
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Let t is the number of 20-cent coins in the purse.
Then the number of the 5-cent coins is (21-t).
20-cent coins contribute 20t cents into the total.
5-cent coins contribute 5*(21-t) cents into the total.
The balance equation is
20t + 5*(21-t) = 225.
Simplify and solve it for t:
20t + 105 - 5t = 225, or
20t - 5t = 225 - 105, or
15t = 120,
t = = 8.
Answer. There are 8 20-cent coins in the purse.
