4. A trader buys oranges at 7 for a rupee and sells them at 40% profit. How many oranges does he sell for a rupee?
a. 3
b. 4
c. 5
d. 6

Answer: C

Explanation:
Cost price of 1 apple = $\dfrac{1}{7}$
Selling price of 1 apple at 40% profit is equal to 140% of its cost price.
Therefore, Selling price of 1 apple = $\dfrac{1}{7} \times 140\% = \dfrac{1}{7} \times \left( {\dfrac{{140}}{{100}}} \right) = \dfrac{1}{5}$
Therefore, 5 oranges are sold are 1 rupee.

5. On selling mangoes at 36 for a rupee, a shopkeeper loses 10%. How many mangoes should he sell for a rupee in order to gain 8%?
a. 25
b. 30
c. 35
d. 40

Answer: B

Explanation:
Selling price of 1 apple = Rs.$\dfrac{1}{{36}}$
Cost price of 1 apple = $\dfrac{1}{{36}} \times \dfrac{1}{{90\% }}$
Therefore, New selling price = $\left( {\dfrac{1}{{36}} \times \dfrac{1}{{90\% }}} \right) \times 108\% $ = $\dfrac{{108}}{{36 \times 90}} = \dfrac{1}{{30}}$
Therefore, For one rupee, he should sell 30 mangoes.

6. A boy buys eggs at 10 for Rs.1.80 and sells them at 11 for Rs. 2. What is his gain or loss per cent?
a. 1.27%
b. 1.01%
c. 1.68%
d. 1.77%

Answer: B

Explanation:
To avoid fractions, let the number of eggs purchased be, LCM of 10 and 11 = 110
CP of 110 eggs = $\dfrac{{110 \times 1.80}}{{10}}$ = Rs. 19.80
SP of 110 eggs = $\dfrac{{110 \times 2.0}}{{11}}$ = Rs. 20.00
Profit per cent = $\dfrac{{20 - 19.80}}{{19.80}} \times 100$ = $\dfrac{1}{{99}} \times 100$ = 1.01%

7. A woman buys apples at 15 for a rupee and the same number at 20 a rupee. She mixes and sells them at 35 for 2 rupees. What is her gain per cent or loss per cent?
a. 2.04%
b. 3.5%
c. 4.4%
d. 5.4%

Answer: A

Explanation:
Suppose the woman buys two lots of (LCM of 15, 20 and 35) = 420 apples.
One apple cost from the first lot = $\dfrac{1}{{15}}$.
420 apples cost = $\dfrac{1}{{15}} \times 420 = 28$
One apple cost from the second lot = $\dfrac{1}{{20}}$.
420 apples cost = $\dfrac{1}{{20}} \times 420 = 21$
Total cost for 840 apples = 28 + 21 = Rs. 49
Selling price of 1 apple = $\dfrac{2}{{35}}$.
840 apples selling price = $\dfrac{2}{{35}} \times 840 = 48$
Loss per cent = $\dfrac{1}{{49}} \times 100 = 2.04\% $

8. Some quantity of coffee is sold at Rs. 22 per kg, making 10% profit. If total gain is Rs. 88, what is the quantity of coffee sold?
a. 44
b. 55
c. 60
d. 70

Answer: A

Explanation:
Cost price of the coffee = $\dfrac{{22}}{{110\% }} = 22 \times \dfrac{{100}}{{110}} = 20$
Profit on one kg of coffee = 22 - 20 = Rs.2.
Let $x$ kgs of coffee sold. So total profit = $2x$.
$ \Rightarrow 2x = 88$
$ \Rightarrow $ x = 44