Respuesta :

sqdancefan

Answer:

  22 quarters

Step-by-step explanation:

Let q represent the number of quarters in the bank. Then 60-q is the number of nickels, and the total value of the coins is ...

  0.25q + 0.05(60 -q) = 7.40

  0.20q + 3.00 = 7.40 . . . . . . . . simplify

  0.20q = 4.40 . . . . . . . . . . . . . . subtract 3.00

  q = 4.40/0.20 = 22 . . . . . . . . . divide by the coefficient of q

There are 22 quarters in the piggy bank.

_____

Check

The other 60-22 = 38 coins are nickels, so the total value is ...

  0.25×22 + 0.05×38 = 5.50 + 1.90 = 7.40 . . . . . . the required amount

mathmate

Step-by-step answer:

Here's a different way to solve the problem, mentally.

Mixture of 60 coins composed of nickels (5 cents) and quarters (25 cents).

Total value = 7.40.

IF all coins were quarters, value would be 60*0.25 = $15

That makes too many quarters.

To conform to the value of $7.40, we need to reduce the mix by $15-7.40 = 7.60.

Each exchange of quarters and nickels reduces the value by $0.25-0.05=0.20.

It takes 7.60 / 0.20 = 38 exchanges.

So there are 38 nickels and 22 quarters.

Otras preguntas