Answer:
She has 12 quarters.
Step-by-step explanation:
You have two unknowns, the number of quarters and the number of dimes. You need one equation per unknown, so you need two equations. One equation deals with the number of coins. The other equation deals with the values of the coins.
The first step is to choose variables. We can go with x and y, but I prefer to choose q and d, so I remember more easily what they represent.
Let q = number of quarters.
Let d = number of dimes.
Let's deal with the numbers of coins first.
"Georgina has 14 more dimes than quarters"
She has q number of quarters, but the number of dimes is 14 more than the number of quarters. d is 14 more than q. Our first equation is
d = q + 14
Now we deal with the values of the coins.
We don't know yet the actual numbers of dimes and quarters, so we use d and q to represent those numbers.
One dime is worth $0.10; d number of dimes is worth 0.1d.
A quarter is worth $0.25; q number of quarters is worth 0.25q.
The total value of the dimes and quarters is the sum of the values of the two sets of coins:
0.1d + 0.25q
We are told "Georgina has $5.60 in quarters and dimes."
This gives us our second equation.
0.1d + 0.25q = 5.6
Now we have a set of two equations in two variables:
d = q + 14
0.1d + 0.25q = 5.6
There are several methods for solving a system of equations. Since the first equation is already solved for a variable, d, we can use the substitution method.
We rewrite the second equation, but we substitute q + 14 for d in the second equation.
Second equation:
0.1d + 0.25q = 5.6
Substitute q + 14 for d:
0.1(q + 14) + 0.25q = 5.6
Distribute on the left side:
0.1q + 1.4 + 0.25q = 5.6
Combine like terms on the left side:
0.35q + 1.4 = 5.6
Subtract 1.4 from both sides:
0.35q = 4.2
Divide both sides by 0.35:
q = 12
There are 12 quarters.
(You are asked only the number of quarters, so you can stop here. I will continue to find also the number of dimes for 2 reasons. 1) You see how it's done, so it will help with other problems. 2) By finding the numbers of dimes and quarters, then we can check if our solution is correct, which I will do below at the end.)
Now we use the first equation, d = q + 14. We substitute 12 for q and solve for d.
d = q + 14
d = 12 + 14
d = 26
There are 26 dimes.
Check:
We check the numbers of coins:
26 - 12 = 14 The number of dimes is indeed 14 more than the number of quarters.
We check the values of the coins:
0.1(26) + 0.25(12) = 2.6 + 3 = 5.6 The value of the coins is indeed $5.60.
Our answer is correct.
