Rearranging formulae

Rearrange 1/u + 1/v = 1/f

to make u the subject of the formula. Give your answer in its simplest form.

There are a number of ways to approach this problem.

By subtracting 1/v on both sides we get 1/u as the subject of the equation:

1/u = 1/f - 1/v

The inverse of the equation can be found to make the subject u:

u = 1/(1/f - 1/v)

This can be simplified by multiplying by fv/fv:

u(fv/fv) = fv/(fv/f - fv/v)

As fv/fv is equal to one, this can be simplified further to give the final answer:

u = fv/(v-f)

Robert S. A Level Maths tutor, IB Maths tutor, GCSE Maths tutor, IB C...

3 months ago

Answered by Robert, a GCSE Maths tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£18 /hr

Karishma D.

Degree: Medicine (Bachelors) - Imperial College London University

Subjects offered: Maths, Chemistry+ 3 more

-Personal Statements-
-Medical School Preparation-

“Hi guys, I'm a first year medical student at Imperial College London. I chose this degree because it indulges my passion for science whilst allowing me to interact with people, putting what I learn in the lecture theatre into practise...”

£18 /hr

Martin L.

Degree: Chemistry (Bachelors) - Warwick University

Subjects offered: Maths, Chemistry


“About Me: I am currently a third-year student studying Chemistry at the University of Warwick; and have had tutor experience at my secondary school. I take a patient approach to tutoring and believe that a lot of the concepts they tea...”

£22 /hr

Gemma P.

Degree: Natural Sciences (Bachelors) - Durham University

Subjects offered: Maths, Chemistry+ 1 more


“About MeI am a first year student sudying Biology and Chemistry as part of a Natural Sciences Degree at Durham University. I have always had a passion for science and teaching, both academically and non-academically, and have a broad...”

About the author

Robert S.

Currently unavailable: for new students

Degree: Engineering Mathematics (Bachelors) - Bristol University

Subjects offered: Maths, Computing


“About Me: I’m a fresher studying Engineering Mathematics at Bristol University. When I was younger, I was neither particularly interested or any good at maths. It was not until GCSE’s that my teacher motivated and inspired me to achie...”

You may also like...

Other GCSE Maths questions

Simplify (3x^2 - 15x)/(3x^2 - 13x -10)

Solve equations 2x+y=9 and x+2y=6 to find x and y.

Find the exact value of the gradient of the curve y=e^(2-x)ln(3x-2) at the point on the curve where x=2.

Solve x^2 + 4x + 4 = 0

View GCSE Maths tutors


We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss