Question

You have 14 coins that are nickles and quarters that equals 2 dollars how do you solve using substitution?

Answer 1

Answer:

The question is incorrect but if half nickels and quarters exist then you could say the answer is 7.5 nickels and 6.5 quarters.

The problem:

14 coins that are either nickels are quarters

The total dollar amount of these coins is 2 dollars

Step-by-step explanation:

Let n be the number of nickels.

Let q be the number of quarters.

We are given that n+q=14 and that .05n+.25q=2.

I'm going to choose to solve the system by elimination.

Multiplying the first equation by .25 gives:

.25n+.25q=.25(14)

.25n+.25q=3.5

So let's line the equations up now:

.25n+.25q=3.5

.05n+.25q=2

---------------------If we subtract the equations, the variable q will be eliminated.                Thus, we will able to solve for the variable n.

.20n+0q=1.5

.20n=1.5

Dividing both sides by .2 gives:

n=7.5

If n=7.5 and n+q=14, then we have 7.5+q=14 by substitution property.

We can subtract 7.5 on both sides giving us:

q=14-7.5=6.5

We cannot have 7.5 nickels and 6.5 quarters but this satisfies the given information.

Check:

7.5+6.5=(7+6)+(.5+.5)=13+1=14

7.5(.05)+6.5(.25)=2

Now, the requested way which is by substitution:

Let n be the number of nickels.

Let q be the number of quarters.

We are given that n+q=14 and that .05n+.25q=2.

We can solve the first equation for either n or q and then substitute that into the other equation allowing us to solve for the other variable.

Let's solve for q by subtraction n on both sides:

q=14-n

We are going to replace q in the second equation with (14-n) giving us:

.05n+.25(14-n)=2

Distribute:

.05n+3.5-.25n=2

Combine like terms:

-0.2n+3.5=2

Subtract 3.5 on both sides:

-0.2n=-1.5

Divide both sides by -0.2:

n=7.5

Since q=14-n and n=7.5, then q=14-7.5=6.5 .

We are already check the solution above.