Inversely proportional? (1 Viewer)

[Scanorama]

I was doing the practice paper and I've never seen this from the textbook

Joanne is organising the Year 12 Farewell Party. She plans to hire a ferry. The cost per person ($C) of hiring the ferry is inversely proportional to the number of people (n).

Hoanne knows that if 80 people attend, the cost will be $40 per person. If only 50 people attend, now much will it cost per person?


I've never seen the term 'inversely proportional' from the textbook or from my teacher, and I have no fucking idea how to do this stupid question. Can someone please help me out

 

[DAAVE]

Ok a quick lesson on proportionality:

If we say something, lets call it 'y', is proportional to something else, 'x', then we mean the following:

y = kx (k is a constant, meaning it doesn't change).

Now if we say something is inverseley proportional to something else we have:

y=k/x

So in your case:

$C = k/n

Now we have to work out the value for k, so we use the information they've given us:

40 = k/80

k = 3200

So now we can rewrite the formula:

C = 3200/n

Now when 50 people attend:

C = 3200/50
C = $160