The box contains 40 coins of pennies, dimes and quarters. The amount of pennies is equal to the number of dimes.

Question

The box contains 40 coins of pennies, dimes and quarters.  The amount of pennies is equal to the number of dimes, and the total value is $3.37.  How man of each denomitions.

Answer 1

       P +     D +       Q = 40      (Total number of coins)

                              P = D       (Number of pennies equal number of dimes)

0.01P + 0.1D + 0.25Q = 3.37   (Total value of coins)

 

Substituting P = D into the first and the third equations yield

     2D +       Q = 40

0.11D + 0.25Q = 3.37

 

Multiplying both sides of the last equation by -4 to eliminate Q and solve for D.

D = 17, Q  = 6.

Note : Substitution will work just fine.

 

So there are 17 pennies, 17 dimes and 6 quarters in the box.