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Hello Fellow Bitcointalk members. Please explain this. Keep in mind I am not good in maths, so please don't be harsh. :P

Lets say an item costs $100, and we want to increase its price by 30% on the current price, The right way would have been

($100x30)/100 + $100 = 130$ right..?

But today i came across a dude, who did things differently. Instead of solving it that way.

He said Lets subtract 30% from 100% and then calculate the new increased price on the new percentage.

100%- 30% = 70% ( new percentage )

so if we divide

$100/70% we should get the same thing as 30% increase right?, well the answer is surprising(to me atleast), instead of $130, we get $142.85

What is happening here?

we should get the same answer shouldn't we? if are dividing the original price by 70% this means we should be getting the 130% of the Original price. That would mean an automatic addition of 30% to the original price. Why are the answers different. Its just bugging me.

Dividing $100 by 70% gives you $1.42. If you want to add 30% to something find out what that 30% is and then add to original price.

no its not same

thats wrong math. your formula is breaking math rule

i give you explaination about this. its only about percent (%)
you call $100 is 100%
if the price start from $ 100 and increase to 30%
so it will be 100% + 30% = 130% price
then it will be $100 x 130% = $130
so bassically if you call 100% for $100, then it will be 130% for $130

so if lets say price is $130 after increase 30%
how to calculate the price before increase 30%?
it will be $130/(100%+30%) = $130/130% = $100
and the price go back like before

He did it wrong. Your first formula is correct though his way of solving is acceptable but not in your case. Subtracting the given percentage in 100%, then use the difference as percentage is mostly used in "discount".

For example:

One branded bag is cost of 700$, taking it cash will guarantee you a 20% discount. In calculation, instead of: 700$ - (700$x20%) =560$, you can use 100%-20%= 80% (basic), apply in the formula 700$ x 0.8 = 560$

30% increase in 100 is 130.
30% decrease in 142.85 is 100.

So, your question should be if a man after giving a discount of 30% sold an item for $100, what would be his marked price?

Shorter way to write the same calculation is:

1,3*100$= 130$
and 1,3 comes from 0,3+1 which is the same as (30%+100%)/100

yes


yes


No, why ?


$100/70% = $100/( (100x70)/100)) = $100/70 = $1.42857...

To get 30% of $100;

100 x 0.3 = $30
100 + 30 = $130


To add 30% on top of $100;

100 x 1.3 = $130