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?

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): You can put this solution on YOUR website!
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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.

Solved.

On many other solved coin problems see the lessons
    - Coin problems
    - More Coin problems
    - Solving coin problems without using equations
    - Kevin and Randy Muise have a jar containing coins
    - Typical coin problems from the archive
    - More complicated coin problems
    - Solving coin problems mentally by grouping without using equations
    - Santa Claus helps solving coin problem
in this site.

You will find there the lessons for all levels - from introductory to advanced,
and for all methods used - from one equation to two equations and even without equations.

Read them and become an expert in solution of coin problems.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Coin problems".

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