Question

Johnny has some nickels and dimes in his pocket, and the change is worth $0.75. He has twice as many dimes and nickels. How many of each type of coin does Johnny have? // system of equations questions it requires 2 equations and to define the x and y

Answer 1

Answer: 3 nickels and 6 dimes

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Work Shown:

x = number of nickels

y = number of dimes

5x = value of the nickels only (cents)

10y = value of the dimes only (cents)

5x+10y = total value of all the coins = 75 cents

One equation we can form is 5x+10y = 75.

"he has twice as many dimes as nickels" tells us that y = 2x. We can replace every copy of y with 2x and solve for x as shown in the steps below.

5x+10y = 75

5x+10(y) = 75

5x+10(2x) = 75 ... plug in y = 2x

5x+20x = 75

25x = 75

x = 75/25

x = 3

This value leads to y = 2x = 2*3 = 6

Johnny has 3 nickels and 6 dimes.

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Check:

1 nickel = 5 cents

3 nickels = 3*5 = 15 cents

1 dime = 10 cents

6 dimes = 6*10 = 60 cents

3 nickels + 6 dimes = 15 cents + 60 cents = 75 cents = $0.75

The answers are confirmed.