Maths

>

GCSE

Ratios

Question

How do you solve inverse proportion questions?

2 years ago

·

2 Replies

·

1509 views

E

Erna Wilderman


2 Answers

William M Profile Picture
William M Verified Sherpa Tutor ✓

Confidence is key, get some with me

Depends on the question but basically: an inverse proportion is just 1/direct proportion.


So if two things have a direct proportion of 2 then their inverse proportion would be 1/2.


For example: 1) If  n varies inversely as m and n=2 when m=21 then find:


     

a) the formula for n in terms of  m:

f direct then n=km but this is inverse so n=k/m. Now find out k by substituting values you


know....2= k/21, multiply both sides by 21 and get k=21x2=42 and the formula is n=k/m so it is


n=42/m

b) the value of  n given  m=2


now we just substitute these values into our equation so n=42/m so n=42/2=21


c) the value of  m given n=1  


now we just substitute these values into our equation and n=42/m so 1=42/m which means m=42 when n=1 by cross multiplying



Hope this helps, just remember inverse proportion=1/direct proportion

 

I'm available for 1:1 private online tuition!

Click here to view my profile and arrange a free introduction.
D
Dawn M

If x is inversely proportional to y, then your first step is to write an equation linking x and y as follows:

x = k/y

Then in the question you will be given a value of y for a given value of x. By substituting both of these into the above equation you can solve it to find k.

I advise that you then rewrite the equation replacing the k with the number you have just found.

Then you may be asked to find the value of x for a given value of y or vice versa, which means you need to substitute in the given value and solve the equation.

Think you can help?

More Maths GCSE Questions
Sherpa Badge

Need a GCSE Maths tutor?

Get started with a free online introductions with an experienced and qualified online tutor on Sherpa.

Find a GCSE Maths Tutor