Math Question.

[Thekool1s]

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

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.

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[baradfo]

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.

[deepblue01]

$100/70% we should get the same thing as 30% increase right?

no its not same

What is happening here?

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

[dracarys_]

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$

[Nalbo]

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?

[aplistir]

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

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

[G.Seed]

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

yes

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

yes

$100/70% we should get the same thing as 30% increase right?

No, why ?

well the answer is surprising(to me atleast), instead of $130, we get $142.85

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

[B!tBoy]

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