Question

a person sold two steel almirah for 1980 rs each. on one he gained 10% while on the other he lost 10%.what he gain or lost in bargain

Answer 1

Let the CP of one almirah = Rs x
A/q,
on gaining 10%
x + 10x/100 =1980
⇒ 11x/10 = 1980
⇒x = 1980×10/11
⇒CP =Rs 1800
now,
on 10% lost,
x - 10x/100 = 1980
⇒9x/10 = 1980
⇒x = 1980×10/9
⇒CP =Rs 2200
total CP = 1800 +2200= Rs 4000
total SP = 1980 ×2 =Rs 3960
∴gain = 4000 - 3960 = Rs 40
∴gain % = (40×100)/4000 = 1%

Answer 2

please see the attachment.in this sum i have used the formula SP = (1+ d/100)CP
 and SP = (1- loss/100)CP to find the CP in both the cases.