SOLUTION: A box contains nickels, dimes and pennies worth $8.40. The number of dimes is six less than twice the number of pennies and there is an equal number of dimes and nickels. How many

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A box contains nickels, dimes and pennies worth $8.40. The number of dimes is six less than twice the number of pennies and there is an equal number of dimes and nickels. How many       Log On


   

Question 1120159: A box contains nickels, dimes and pennies worth $8.40. The number of dimes is six less than twice the number of pennies and there is an equal number of dimes and nickels. How many nickels are there in the box?
Found 3 solutions by josgarithmetic, MathTherapy, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
A box contains nickels, dimes and pennies worth $8.40. The number of dimes is six less than twice the number of pennies and there is an equal number of dimes and nickels. How many nickels are there in the box?
Let number of nickels be N, and number of pennies, P

Then number of dimes also = N

We also get: Number of dimes, or 

We now get: matrix%281%2C3%2C+.05N%2B+.1N+%2B+.01%28%28N+%2B+6%29%2F2%29%2C+%22=%22%2C+8.4%29 

matrix%281%2C3%2C+.05N%2B+.1N+%2B+%28.01N+%2B+.06%29%2F2%2C+%22=%22%2C+8.4%29 

.1N + .2N + .01N + .06 = 16.8 ------- Multiplying by LCD, 2

.31N = 16.74

Number of nickels, or highlight_green%28matrix%281%2C5%2C+N%2C+%22=%22%2C+16.74%2F.31%2C+%22=%22%2C+54%29%29

Answer by ikleyn(52786) About Me  (Show Source):
You can put this solution on YOUR website!
.
This problem is a typical example to solve using  ONE  UNKNOWN  and  ONE EQUATION,  as the tutor  @MathTherapy did.


The way  @gosgarithmetic  uses is the way to nowhere.

I do not recommend you to follow his approach.

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If you want to see other similar problem solved with one equation and one unknown,  look into the lessons
    - Advanced word problems to solve using a single linear equation
in this site.