How do I determine the dependent variable and independent variable of these relations?

Question

anonymous · Answer

a) the time it takes to drive 100 km and the speed of the car

anonymous · Answer

b) the ages of students and the numbers of CDs they own.
c) the number of tickets sold for a school play at $8 per ticket and the revenue from ticket sales.

anonymous · Answer

Time and distance are independent.Velocity is dependent on time and distance

anonymous · Answer

can you please explain why it is independent variable and why it is dependent?

anonymous · Answer

Velocity is the amount of distance travelled in 1 second which shows why it is dependent on distance and time.But distance is not dependent on anything

anonymous · Answer

how about for the other relations?

amistre64 · Answer

in general, you try to make the independant variable the one that has a steady rate of change; time, ticket price, aging are all pretty steady rates of change

amistre64 · Answer

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phi · Answer

This can be a bit tricky, but in general there is a best choice as to which is dependent and which is independent.

for (a) we have two choices:
The time of a trip depends on your speed
Your speed depends on the length of the trip

Does one of the choices make more sense to you?

for (b)
Age depends on how many CDs you have
# of CDs depends on teen's age

for (c)
$ brought in depends on # of tickets sold
# of tickets sold depends on how many $ were brought in

Can you choose which pair makes more sense?