Question

A man sold a phone at 10% gain if he had bought it at 20% less and sold it at Rs10 more he would have gain 40% find the cost price

Answer 1

Let original CP of the phone was X.

First Case:
SP = X + 5% of X = 105X/100
Second Case:
He bought phone at 5% less.

CP = X - 5% of x = 95X/100
SP = (105X/100) - 1
Gain 10%.

SP - CP = Gain
(105X/100) - 1 - 95X/100 =  10% of 95X/100

10X/100 -1 =  95X/1000

0.1X - 1 =  0.095X
0.005 X = 1
X = 200

So, Original CP was Rs. 200.