Help me double check on some simple algebra II questions?

Question

3. The germination rate for zinnia seeds is 78%. This means that, on average, 78% or the seeds will sprout and grow into plants.

Q: What is the independent variable? What is the dependent variable?
A: independent: germination rate
Dependent: seeds

Q: Express this relationship as a function.
A: f(x) = .78x

Q: What is the domain of this function? What is the range?
A: x is greater then or equal to zero
Y is greater then or equal to zero
Q: If Jim wants 60 plants for his yard, how many seeds should he plant?
A: x = 77

4. It costs $25 a day plus $.06 per mile to rent a car.
Q: What is the independent variable? What is the dependent variable?
A: independent: days
Dependent: cost

Q: Express this relationship as an equation.
A: f(x) = 25x + .06

Q: What is the domain of this function? What is the range?
A: x is greater then or equal to zero.
Y is greater then or equal to .06

Q: What is the greatest number of miles you can drive in a day if you have $40
A: x = 1.5976

Answer 1

The first answer is correct.

The second answer is correct.

The third and fourth are correct.

Yup, the fifth is correct, too.

Just say that y= 25d + .06m

That's right.

40 = 25d + .06m
40 = 25(1) + .06m
40 = 25 + .06m
15 = .06m
Divide both by .06.
250 = m

I have no clue what you did for that last one.

Answer 2

3. Your are missing something. An independent variable is one you can CONTROL. The dependent variable is one you calculate from your relationship. You can CONTROL the number of seeds planted. You calculate the number of plants germinated from the relation:
G = 0.78 P
4. You aren't conceptualizing what's going on. There are TWO independent variables. You can control the number of days(D) you keep the car and you can control the number of miles you drive(M). So the cost equation is .................................. C(D,M) = 25*D + 0.06M