SOLUTION: Ngo has a collection of dimes and quarters with a total value of $3.20. The number of dimes is 4 more than the number of quarters. How many of each coin does he have?
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Question 1080283: Ngo has a collection of dimes and quarters with a total value of $3.20. The number of dimes is 4 more than the number of quarters. How many of each coin does he have? Answer by ikleyn(52803) (Show Source):
Let me tell you how to solve this problem MENTALLY.
Take off 4 dimes from the collection (mentally).
Then the new collection consists of equal number of dimes and quarters and is worth 280 cents.
Now you can group the coins in updated collection in sets/pairs consisting of 1 dime and 1 quarter.
Each pair is worth 10 cents + 25 cents = 35 cents.
How many pairs do you have ? - But of course, = 8.
(I am sure you can calculate it mentally).
From here, there is only one step to get the
Answer: There are 8 quarters and 8+4 = 12 dimes in the original collection.
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