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

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 D

Explanation:

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

Answer: Option A

Explanation:

This type of question can be easily and quickly solved as following:

Let at Rs x it can earn 15% pr0fit
85:18700 = 115:x [as, loss = 100 -15, Profit = 100 +15]

x = (18700*115)/85
= Rs.25300

Answer: Option A

Explanation:

Please note in this type of questions, get the value of 1 kg to solve this question, lets solve it.

C.P. of 1 Kg = 420/70 = Rs. 6
Selling Price = 6.50
Gain = Rs. 0.50

\begin{aligned}
Gain\% = \frac{.50}{6}*100 \\
= 8\frac{1}{3}\%
\end{aligned}

Answer: Option C

Explanation:

We need to get the Total selling price to solve this question. Because after getting selling price we can get profit or loss, then we can calculate profit% or loss%

So lets solve this:

Price Received by selling one fourth of the material at a loss of 20% =
(1/4) * 600 * (80/100) = Rs. 120

Price Received by remaining material at a gain of 10% =
(3/4) * 600 * (110/100) = Rs. 495 [Note: 1-(1/4) = 3/4]

Total Selling Price = 120 + 465 = Rs. 615

Profit = 615 - 600 = 15

\begin{aligned}
Profit\% = \left( \frac{Gain}{Cost} * 100 \right)\% \\
= \left( \frac{15}{600} * 100 \right)\% \\
= \frac{5}{2}\% = 2\frac{1}{2}\%
\end{aligned}