Discounted upcharge

You should pay 20% less than 20% more, because the "20% less" applies to a larger total amount than the "20% more".

Formally,

if the amount is $x$

then 20% more is $(1 + 0.20)\ x$

and 20% less than that is $(1 - 0.20)\ (1 + 0.20)\ x$

which is equal to $0.80 \cdot 1.20\ x = 0.96 x$ .

Thus paying 20% less than 20% more than the original price is actually a discount of 4%. Take it!

You can logically deduce that 20% less on a larger amount will discount more. Just for certainty, I used a base of 100 as the original price. 100+(100*0.2)=120. 20% off 120 is equal to 120-(120/5) which is 120-24 which gives you 96% of the original price.

If the original price is 100 dollars, 20% would be 20 dollars. 20% of 120 dollars is 24 dollars. 100 - 24 = 96!

20% less than 20% more is better than the exact value. Here's my example- let's say you offer 50,000 dollars to your friend for his car. If you go for 20% less than 20% more, it will be:

=(50000 *120%) *80%

=60000*80%

=48000

This would result in you paying 96% of your original price. Same goes to other values.