Question

A student buys a pen for Rs 90 and sells it for Rs 100. Find his gain and gain percent.

Answer 1

Hint: Use the fact that gain is equal to cost price subtracted from selling price, i.e. gain= S.P -C.P. Gain % is the amount of gain per 100 units of C.P. Using a unitary method find the gain % of the student in this whole transaction. Alternatively, use $gain\%=\dfrac{gain}{C.P}\times 100$ to get the gain% earned by the student in this transaction.

Complete step-by-step answer:
We have the cost at which the pen was purchased by the student = Rs. 90
The amount for which the pen was sold by the student = Rs. 100
Hence the gain earned by the student = Rs 100-Rs 90 = Rs. 10
Hence the gain earned by the student is equal to Rs.10
Gain % is defined as the amount of gain earned per 100 units of cost price.
We have, the gain on Rs 90 of C.P = 10
Hence, we have
The gain on Re. 1 of C.P $=\dfrac{10}{90}=\dfrac{1}{9}$
Hence gain per Rs. 100 of C.P $=\dfrac{1}{9}\times 100=11.11$
Hence the gain %age of the student = 11.11%

Note: [1] We can directly calculate gain using the formula
$gain\%=\dfrac{gain}{C.P}\times 100$
Substituting the values of gain and C.P, we get
$gain\%=\dfrac{10}{90}\times 100=11.11\%$