how do you find the original price of something that has been changed by a percentage decrease

Lets say something has been decreased in price by 20% and is now £40. The tempting thing to do here is to find 20% of 40 and add it back on, but this is not okay! The reason we can't do this is that 20% of 40 is different to 20% of the original, bigger number. Instead, think of our original number as 100%. We took away 20% so now we have 80% left, how can we get back? well, if we divide 80% by 4 we get 20%, then multiply it by 5 we get 100%! Do the same to the £40, which is our 80%, and you will get back to the original. I like to draw a grid

80% = £40

divide by 4

20% = £10

multiply by five

100% = £50

Steven K. GCSE Maths tutor, A Level Maths tutor, Mentoring -Personal ...

2 years ago

Answered by Steven, a GCSE Maths tutor with MyTutor

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


£20 /hr

Eszter H.

Degree: Modern Languages (Bachelors) - Durham University

Subjects offered:Maths, History+ 6 more

English and World Literature
English Literature
English Language
.MLAT (Modern Languages)

“I am a Modern Languages (German and Spanish) student at Durham University. I believe that the knowledge of foreign languages is becoming more and more important, thus I am devoted to help every student who want to develop their German...”

£22 /hr

Lauren G.

Degree: Technology Enhanced Learning (Masters) - Durham University

Subjects offered:Maths, Physics+ 2 more


“Hello! I'm currently a Master's student studying Technology Enhanced Learning at Durham University. I completed my undergrad last year in Natural Sciences with Maths and Computer Science, also from Durham.  I am very passionate about ...”

£20 /hr

Shreya G.

Degree: Biochemistry with molecular medicine (Bachelors) - Nottingham University

Subjects offered:Maths, Biology+ 1 more

-Personal Statements-

“I am a first year undergraduate student at The University Of Nottingham, currently studying Biochemistry with molecular medicine. ”

About the author

Steven K. GCSE Maths tutor, A Level Maths tutor, Mentoring -Personal ...

Steven K.

Currently unavailable: for regular students

Degree: Material Science (Masters) - Oxford, The Queen's College University

Subjects offered:Maths, -Personal Statements-

-Personal Statements-

“I started tutoring through my father who is a maths teacher, as he would pass on requests for lessons to me. Through my A levels I tutored GCSE maths, and began to also teach physics, chemistry and biology, the other subjects i was st...”

You may also like...

Posts by Steven

how do you find the original price of something that has been changed by a percentage decrease

What's the difference between ionic and covalent bonds?

Why do we need active transport if we have Diffusion?

Other GCSE Maths questions

Factorise x²+5x+6.

Expand (2x-3)(4x+4) using the FOIL method.

Expand and simplify 3(2x + 5) – 2(x – 4)

How do I know how many solutions a quadratic equation has?

View GCSE Maths tutors

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