Question

By selling 12 glasses for Rs.600 a shopkeeper makes a profit of 25%. Find his profit or loss percent when he sells 15 glasses for Rs.540.

Answer 1

S.P. of 12 glasses
= Rs.600
S.P. of 1 glass
= Rs.`(600)/(12)`
= Rs.50
Profit = 25%
`"S.P."/"C.P" = 1 + "Profit"/(100)`

⇒ `(600)/"C.P." = 1 + (25)/(100)`

⇒ `(600)/"C.P." = (125)/(100)`

⇒ C.P. = `(600 xx 100)/(125)`
= Rs.480
C.P. of 12 glasses
= Rs.480
C.P. of 1 glass 
= Rs. `(480)/(12)`
= Rs.40
C.P. of 15 such glasses
= Rs.40 x 15
= Rs.600
S.P. of 15  glasses
= Rs.540
∵ C.P. > S.P.
There is a loss of C.P. -  S.P.
= Rs.(600 - 540)
= Rs.60
Loss %
= `"Loss"/"C.P." xx 100`

= `(60)/(600) xx 100`
 = 10%.