Question

Mrs. Santos is buying binders for the students in her class. She determined that 15 binders would cost $22.50.

Cost of Binders
On a coordinate plane, a graph titled Cost of Binders has number of binders on the x-axis and total cost in dollars on the y-axis. The line goes through points (0, 0) and (15, 22.5).

If all of the binders cost the same amount, which statement is true?
It will cost $12 for 18 binders.
It will cost $20 for 30 binders.
It will cost $42 for 28 binders.
It will cost $48 for 48 binders.

Answer 1

$42 for 28 binders.

Explanation:

B

Answer 2

It will cost $42 for 28 binders

Explanation:

We know that 15 binders = 22.50 dollars . We need to find the cost of 18, 30, 28, and 48 binders to figure out if they match up with the statements. One way to do this is to find the cost for one binder, and then multiply that by the number of binders to find the cost for a certain number of binders. For example, if one binder costs 2 dollars, five binders would cost 2 * 5 = 10 dollars.

To figure out how much one binder costs, we can use the division property of equality to divide both sides of our equation (15 binders = 22.50 dollars) by 15. We divide by 15 because anything divided by itself is equal to 1, and that would make it 1 binder = something dollars.

Applying this, we get

(15 binders)/15 = (22.5 dollars)/15

1 binder = 1.5 dollars

For 18 binders, this would cost 1.5 * 18 = 27 dollars. We know this because we add 1.5 dollars for each binder.

For 30 binders, this would cost 30*15=45 dollars

For 28 binders, this would cost 1.5 * 28 = 42 dollars

For 48 binders, this would cost 1.5*48 = 72 dollars

The only one that matches up is 28 binders for 42 dollars