Question

The total cost of gasoline varies directly with the number of gallons purchased. Gas costs $1.89 per gallon. Write a direct variation to model the total cost c(g) for g gallons of gas.
A. g = 1.89g
B. c = g + 1.89
C. c = 1.89g
D. c = g/1.89

Answer 1

Here, (c)ost and (g)allons vary directly so we have:

c = k times g

And since we have the price per gallon, we have that "k" -> 1.89

So,

c = (1.89)(g)

Answer 2

Also,

cost = (cost/gallon)(gallons)

See how "gallons" cancels to give just "cost on both sides?

Answer 3

Yes :D

Answer 4

"c" and "g" are on opposite sides here because as gallons increases, so does cost.

Answer 5

So, what kind of math is this we've been doing?

Answer 6

This is proportions, a branch of arithmetic/algebra. Also known as ratios.

You could also have looked at it as:

c/g = 1.89

As c goes up, so does g, to keep a constant 1.89

Answer 7

that makes sense

Answer 8

ready for the next?

Answer 9

At some point, I'm going to bail because I'm having trouble with my eyes. But just post a new thread and someone will come there.

Answer 10

Do you have glasses and just don't use them or have you just been up too late?

Answer 11

I'm 55 and have recently been diagnosed with an actual disease/disorder called "dry eye". It's horrible.

Answer 12

oh let me get the next question

Answer 13

ah man that sucks D:

Answer 14

I can't imagine what you're going through but I hope the best for you

Answer 15

It's life. I try not to complain.

Answer 16

Thx much!

Answer 17

Anytime