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Exponential graph GCSE past papers question

I'm having some trouble with the question in the picture. I used some trial and error to find an answer, but I'm sure there must be another way of doing it. Any ideas? Thanks.

Reply 1

Zacken

You have two points, let's use the first one:

5 = pq

and

320 = pq^4 = pqq^3 = 5q^3 \Rightarrow q^3 = \cdots

Reply 2

Lelanor

Original post by Zacken

You have two points, let's use the first one:

5 = pq

and

320 = pq^4 = pqq^3 = 5q^3 \Rightarrow q^3 = \cdots

Thanks! I've worked it out now using that to form the equation 320/q^3=5 and solving it.

Reply 3

Zacken

Original post by Lelanor

Thanks! I've worked it out now using that to form the equation 320/q^3=5.

Do you mean

\displaystyle q^3 = \frac{320}{5} = 64 = 4^3

Reply 4

Lelanor

Original post by Zacken

Do you mean

\displaystyle q^3 = \frac{320}{5} = 64 = 4^3

Well, I did this:
320/q^3 = 5
320 = 5q^3
q^3 = 64
q = 4
But that's pretty much the same thing.

Reply 5

Zacken

Original post by Lelanor

Well, I did this:
320/q^3 = 5
320 = 5q^3
q^3 = 64
q = 4
But that's pretty much the same thing.

Fair enough. You cool with the method?

Reply 6

Lelanor

Original post by Zacken

Fair enough. You cool with the method?

Yep, your first post nudged me in the right direction. I realised I'd have to form some kind of equation(s) but I just couldn't work out what, so thanks :smile:

Reply 7

Zacken

Original post by Lelanor

Yep, your first post nudged me in the right direction. I realised I'd have to form some kind of equation(s) but I just couldn't work out what, so thanks :smile:

Awesome, glad I helped.