Question

oranges were bought at 7 for rs 3 . at what rate per 100 must they be sold to gain 33%.

Answer 1

Cost Price of 7 Oranges = Rs 3 
Cost Price of 100 Oranges = ( 3 × 100 ) / 7
C.P = Rs 300 / 7
Let Selling Price of 100 Oranges = S.P
gain ( g ) = 33%
We know that ,
S.P = C.P × ( 100 + g ) / 100
= ( 300 / 7 ) ( 100 + 33 ) / 100
= ( 300 × 133 ) / ( 7 × 100 )
= 3 × 19
= Rs 57
He has to sold the 100 Oranges 
at Rs 57 to gain 33%.