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:

Let the C.P. = x,
Then S.P. = (120/100)x = 6x/5
New S.P. = 2(6x/5) = 12x/5

Profit = 12x/5 - x = 7x/5

Profit% = (Profit/C.P.) * 100
=> (7x/5) * (1/x) * 100 = 140 %

Answer: Option D

Explanation:

Here always remember, when ever x% loss,
it means S.P. = (100 - x)% of C.P
when ever x% profit,
it means S.P. = (100 + x)% of C.P

So here will be (100 - x)% of C.P.
= 80% of 1200
= 80/100 * 1200
= 960

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 B

Explanation:

Please remember
\begin{aligned}
S.P. = \left( \frac{100+gain\%}{100} * C.P \right)\\
\text{So, C.P. = }\left( \frac{100}{110} * 25.75 \right)\\
\text{When S.P. = 25.75 then } \\
Profit = 25.75 - 25 = Re. 0.75 \\

Profit\% = \frac{0.75}{25} * 100 = 3\%

\end{aligned}