If the cost price of 12 pens is equal to the selling price of 8 pens, the gain percent is ?

Answer: Option B

Explanation:

We Know,

\begin{aligned}
S.P. = \left( \frac{100+gain\%}{100} * C.P \right)\\
=> C.P. = \frac{100}{122.50}* 392 \\
= 320 \\

Profit = 392 -320 = Rs 72
\end{aligned}

Answer: Option A

Explanation:

Suppose he bought 5 kg and 3 kg of tea.
Cost Price = Rs. (5 x 18 + 3 x 20) = Rs. 150.
Selling price = Rs. (8 x 21) = Rs. 168.
Profit = 168 - 150 = 18

So, Profit % = (18/150) * 100 = 12%

Answer: Option D

Explanation:

85 : 9 = 105 : x
x= (9×105/85)
= Rs 11.81

Answer: Option B

Explanation:

Question seems a bit tricky, but it is very simple.
Just calculate all Cost price, then get 150% of CP.

C.P. = 10000 + 5000 + 1000 = 16000

150% of 16000 = 150/100 * 16000 = 24000

Answer: Option C

Explanation:

Whenever we get this type of question, we should have formula in mind that,
Gain% = (gain/cost)*100

Cost = 4700 + 800 = Rs. 5500
S.P. = Rs. 5800

Profit = 5800 - 5500 = 300
\begin{aligned}
Gain\% = \frac{300}{5500}*100 \\
= 5\frac{5}{11}\%
\end{aligned}