A man gains 20% by selling an article for a certain price. If he sells it at double the price, the percentage of profit will be.

Answer: Option D

Explanation:

In this type of question, we will first find total C.P. of items, then total S.P. of items, then we will get gain or loss. From which we can easily calculate its percentage.

So lets solve it now.
\begin{aligned}
\text{So, C.P. of 1st transistor = }\\
\left( \frac{100}{120} * 840 \right) = 700 \\

\text{C.P. of 2nd transistor = }\\
\left( \frac{100}{96} * 960 \right) = 1000 \\

\text{Total C.P. = 1700 }\\
\text{Total S.P. = 1800 }\\
\text{Gain = 1800 - 1700 = 100}\\
\text{Gain% = } \left( \frac{100}{1700} * 100 \right) \\
= 5\frac{15}{17}\%
\end{aligned}

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 C

Explanation:

Let the cost price 1 article = Re 1
Cost price of x articles = x
S.P of x articles = 20

Gain = 20 -x

\begin{aligned}
=> 25 = \left( \frac{20-x}{x} * 100 \right) \\
=> 2000 - 100x = 25 x \\
=> x = 16
\end{aligned}

Answer: Option C

Explanation:

So before solving this question we will get the C.P. and S.P. of 1 article to get the gain percent.

C.P. of 1 orange = 350/100 = Rs 3.50
S.P. of one orange = 48/12 = Rs 4 [note: divided by 12 as 1 dozen contains 12 items]
Gain = 4 - 3.50 = Rs 0.50
\begin{aligned}
Gain\% = \frac{0.50}{3.50}*100 \\
= \frac{100}{7}\%
= 14\frac{2}{7}\%
\end{aligned}

Answer: Option D

Explanation:

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