Question 72434
<pre><font face = "lucida console" size = 4><b>Bob paid for his breakfast with 36 coins 
consisting of dimes and quarters. if the bill 
was 4.50 then how amny of each type of coin 
did he use.

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Two ways to solve.  Use whichever one you are
presently studying:

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Method 1. Using one unknown

Let Q = the number of quarters.

Then to find the number of dimes, use the formula

(SECOND NUMBER) = (TOTAL OF BOTH NUMBERS) — (FIRST NUMBER)

so

NUMBER OF DIMES = 36 - Q

The value of all the quarters = .25Q

The value of all the dimes = .10(36 — Q)

Value of quarters + Value of dimes = $4.50 

                .25Q + .10(36 — Q) = 4.50

Solve that for Q and get Q = 6, then use
 
NUMBER OF DIMES = 36 - Q = 36 - 6 = 30

So the answer is 6 quarters and 20 dimes.

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Method 2. Using two unknowns:

          D + Q = 36
    .10D + .25Q = 4.50
  
Solve that system and get D = 30, Q = 6

Edwin</pre></font></b>