GCSE Maths - Reverse Percentages - Calculating The Cost Before The Discount #96

[@Cognitoedu]

If you’d like to practise the material covered in this video, check out our platform at www.cognitoedu.org - it's totally free, and has been built to make learning and revision as easy as possible. The main features are: - Lessons organised by topic, only the lessons relevant to your specific exam board and tier are shown. - Automatic progress tracking. Progress bars tell you what you’re doing well at, and what you need to spend some time on. - Practise quizzes so you can test your knowledge. You can quiz yourself on any combination of topics you like. - A huge number of fully-hinted questions that take you step-by-step through some of the trickiest calculations & concepts. - A comprehensive bank of past exam papers, organised both by year, and also by topic. Amadeus & Tom

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[@noel7777noel]

Other tricks of math backward. Math backwards also is 125% of 16 is 20. But 80% of 20 is 16. Another trick of math backward is divide labor hours by inflation to adjust for inflation. I mean. Math done forward can be done backward. Say you wanted to know how much inflation would happen if the auto workers wanted a 25% raise. Say they had a 5% raise while automobiles have gone up 30%. 0/4 = passive income investors + 8/4 = active income workers = 2 = 8/8 = total GDP The active income fraction equals two. these two mean they have to work twice as longer at work to make up the investors not working. This is represented by the zero. 8/8 represents a whole pie. And 8/4 represents the workers' slice of the pie. And 0/4 represents the passive income investors' slice of the pie. Well, first, let's look at at 5% raises that caused 5%inflation backward. Let's apply the 5% raise. 4 × 1.05 = 4.2. 0/4 = passive income investors + 8.2/4.2 = workers = 1.95 = 8.2/8.2 = total GDP Notice tge GDP went up with inflation. 8.2 / 8 = 1.025. 2.5% inflation happened. As you can see, the workers' hours went up to 8.2 from 8. This doesn't mean the workers have to work more hours at work. This is adjusted for inflation. So now the workers only have to work 1.95 times as many hours at work, down from 2. Now, let's add the 25% economic iniquity. The automobiles have gotten 25% more expensive. 4.2 × 80% = 3.36 Notice I did the 125% backwards and applied 80%. 0/4.84. Passive income investors + 8.2/3.36. Workers = 2.44 = 8.2/8.2 Notice that the workers now have to work 2.44 times as many hours at work. From 1.95 1.95×125%= 2.44 Now the workers want a raise of 25% because automobiles have gotten 25% more expensive. So, let's find out how much inflation happens. Any guesses? The workers raise of 25% 3.36 × 1.25 = 4.2 0/4.84. The investors + 9.04/4.2. The workers = 2.15 = 9.04/9.04 So 9.04 divided by 8.2 equals 1.10. So. This 25% raise only caused 10% inflation. But the workers didn't go back to only working times 2 as many hours at work. Hold on now. Peter was after 44% rsise to go back to normal. 3.36 × 144% = 4.8384 0/4.84. Passive income + 9.67/4.83. The workers = 2 = 9.67/9.67 GDP That's better. The workers' slice of the pie is back to 2. And 9.67/8 is 20% inflation. And for extra credit. How did I come up with the 44% raise to know the fraction would equal 2.

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[@sallyread5437]

I’m helping my daughter with her gcse (she isn’t at school in England but has to do it for an upcoming move). I’ve never been able to do maths and my daughter hates it. But we LOVE this channel. It’s the only one makes any sense. Brilliant ❤

[@pwarrow8858]

The fact that you explain why each step is the way it is and how it relates to the funtion and not just show me how to solve it, is exactly what I needed. Thank you so much for this you are a life saver.

[@LapissHamster]

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[@rawsushi5302]

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[@studyskillz6404]

Thank you Cognito for keeping students going through this tough time! Much love :)

[@jacobbillups4715]

PSA for anyone who conceptualizes these problems from a different angle here is a different way to get the same answers (of course the way in the vid is completely valid this is just an alternative). If you think of the percentages as pure decimals you can often cut a few steps. For example the first problem where the house is increased by 15% to £207,000. Your target is the original 100%. So you can do it in one step by taking £207,000/1.15=£180,000. Same method for example 2: 20% sale with new price at £72.00 (100% OG price the target again). So this time you’d take £72/0.80=£90.00. Only one that is a tad counterintuitive is the one where you are given the % and the change in price but neither original nor new total. In that case you take that price change (delta) and divide it by the % given in decimal form (sounds complex but really easy in practice). So for the example problem 5% increase=£42.50. Take £42.50/0.05=£850. Then finally since 850 is the OG price you’d add that £42.50 on top for the £892.50 new price. Lastly to drive the point home let’s say that problem was the same but it was a decrease/discount instead. Everything would be the same save the last step where you’d subtract the 42.5 from 850 in the end. Side note with any problem like this it’s easy to accidentally flip things around so a good practice is to mentally check yourself as you go by asking if the number you just got makes sense. Like if you multiply the first problem by 1.15 instead of dividing it. You end up with a number higher than the 207k you started with (which makes no sense lol). I doubt anyone will have read all that but if by some miracle you did and it helped lmk lol 😊

[@Nehselo]

thankyou you explained it very well

[@ZainaDalal-tv3xk]

This was exactly what I was looking for, Ty ❤

[@Ivy-xd4hd]

i have a math exam in a week and i’m panicking. it’s safe to say that you just saved my life and sanity, thanks!

[@readerofmanga]

The first time I came across this, I managed to learn it quickly and got it right away. Realistically, I will have to revise more on this one.

[@Right_Sune]

👌

[@missesnoku3220]

there’s a much easier way!!! Just divide the number (207,000) by how much the percent changed as a decimal (1.15) !! pleaseee this way is so much easier especially in calculator exams.

[@missesnoku3220]

try it in a calculator! it does work! it still equals 180,000 , your welcome!

[@ItzM3LTED]

Ty❤

[@AzeezOng]

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[@Cognitoedu]

Great to hear you found it easy to watch and digest! 😊

[@MazzBagel]

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what did u get

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Clearly and easily explained. Thank you, Sir!

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hiii i love your videos, they're super helpful! but i was wondering if you could consider making videos on gcse additional maths/ calculus? it would be really really helpful for us :))

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This help me so much tomorrow is my paper and i hope i will score 80 person.

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Really helpful channel for those studying gsce maths/ science.

[@kaurypto9302]

Wow this has made so much sense, thank you. How would you work out a question when it asks you for example: " X buys a watch for £84 which includes a VAT rate of 20%"... How would I work out how much the watch costs without VAT. Sorry if its already been explained. I am studying for Functional Skills Level 2 and find your videos so helpful.

[@chrismafico]

On the first example: instead of doing 270,000 x 115 just to find one percent then having to do more to get the answer, you can just do 270,000 x 115% o your calculator and it will give the end answer for you (there's a % button if you press shift and then answer on your calculator)

[@ezmonke5645]

thank this will help for my next maths test

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I learned well here! You are a good teacher! Liked and subscribed!

[@Cognitoedu]

Thanks Benjamin, glad the video helped 👍

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Thanks, needed a refresh.

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I am proudly announcing that the 1st like of this vid is from me.

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And the third by me

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Yep 👍

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@@deemedepic7721 uhh I was the third like…..

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@@SenyorCaramelo That heart from Cognito probably belonged to you then, sorry!

[@deemedepic7721]

I'm one of the 572 people who liked it so I guess that's good?

[@mnu1401]

the method that i use is based on the car depreciating question n x 0.92 = 12,880 where n is the original value of the car n = 12,880/0.92 n= 14,000

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i have math exam tomorrow and you just saved me

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Hello hope all is well? First I want to thank you for giving free Online Education to the people and for making great content. My question is when you read the problems What questions Can one asked themselves to place the clues we have from the problem?

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So helpful for my maths test tmrw tysm

[@lemondbaby]

For decrease OG = price divided by % = (n) (N) x 100 = answer 8.10£ x 18% = 0.45 0.45 x 100 = 45

[@AhmadAsifArifeen]

this is amazing now i learned finally the trick thanks a lot now I can teach better

[@DanHaines-kw3bl]

another way of doing it is: 1.15x=207000 207000/1.15=x X=180000

[@nouraalmansour7516]

Love your channel it has very effective explanations, obviously I understand more than school

[@lemondbaby]

OG= % + 100 = (number) (Number) divided by price= I did this for the first one 15+100 = 1.15 1.15 divided by 207,000 = 180,000

[@thatgirlkiwii]

Question: The price of a mobile phone increases by 15%. The price of the mobile phone after the increase is $391 What was the price of the mobile phone before the increase? The marking scheme says you only do 391÷1.15=340 They never divided by 100 so I am confused

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Thanks Linda, glad to hear you like it 👍

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[@charliechalk]

For the first question, you can do £207,000 / 1.15 to get £180,000.

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, thank you so much wala God of math

[@fatmaahmad9661]

Thnk u it has really helped

[@samuellacobbinah]

5:59 It makes sense But I don't understand why the percentage change 5%= £42.65 Was divided by 5 to get 1% Why was that done ?

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Thanks It Helped Me Alot❤

[@flamejay7933]

Also helped me too. Amazing video.

[@LB-id3qx]

Nice, I get it but will need to refresh tomorrow.

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Please make video on probability

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Last math exam tomorrow 🎉🎉

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Thank you sir

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Thank you so much

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thank you

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why cant the last question be done like the first one?

[@mrpearcemaths2140]

I really love the art in your videos but it must take you ages to draw! From a subject point it might be worth covering questions where you need to change the units e.g. a 400ml and 1.2l bottle as often students will mindless use them as they are. The same in the cost as exam questions often use say one item at 95p and another at £1.20 to test consistent use of units. You also have questions that are difficult to solve by finding cost per £ etc but far easier to find a cost of an equivalent quantity. E.g. 4pints and 6 pints of milk might provide decimals when you divide but are probably fairly easy to compare if you just take 12 pints of each deal.

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@Cognito can u upload a video on upper and lower bound

[@manishramkumar8948]

wowww, Very Very Nice. I understood the concept

[@Cognitoedu]

Glad we could help Manish! 😊

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THANKS A LOT!

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Thankyou!

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loved it

[@jerryy538]

if it took 57 seconds to do something. now it takes 11 seconds to do that. to find the % of how much better it is. do i 57/11x100? =518% more efficient ? or is that wrong? sorry it's been a while since i did much math. appreciate any help.

[@ryze5436]

Not one dislike Such good work well done 👍

[@fatemaswidan8877]

TYSM

[@TheMrsGypsy]

Thank you so much! 💓 Question - is calculator allowed on these types of questions in the exam?

[@BruhMoment-gm8zc]

Depends on your teacher.

[@ellie-di7cv]

it could be on the calculator or the non calculator exam for gcse :)

[@zakyrabbani7194]

@@ellie-di7cv both papers allow calculator in gcse

[@glxsyy.Yuko4]

Quickest way to understand: divide the price £ by the percentage % and then the answer from that, times it by 100

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This is for learning math.

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How do you do it without a calculator??

[@anime_simpqueen1659]

i was crying because everyone in my class said how simple it was and i could never understand it but now im literally a pro at it thanks to your videos

[@Cognitoedu]

Glad we could help you out 👍

[@Black_Mn850]

wait on the first one cant you do 207,000 divided by 1.15

[@IbrahimAhmed-hj2fp]

I think the new price will be 36.9 because 100-18=82. 82*0.45=36.8 right . If i am right please comment

[@IbrahimAhmed-hj2fp]

Sorry is 36.9

[@shahymohamed5087]

You are pro

[@RhoyaWRLD]

my teacher confused me as we'd use both diving by like 1.1 and I'm very confused still but this method is easier for me

[@Beck2008]

will be doing my gcse in 2025 really need a grade 7 in maths

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GCSE MATH? I had to do this for my 11+ !

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How did it go?

[@eg5240]

Thank you so much!!!!!!!!!!!!!!!

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thanks

[@optify_xltd3210]

I'm still watching

[@twendo7310]

Nice I was struggling in maths

[@probsloms]

3:03 revising for a progress check in y9 set 1 rn lol they give us gcse papers, and why is a pair of sunglasses £72 lol thats a ripoff just saying