Question

a publisher sells a book for rupees 168 at a profit of 20% if is cost of production increases by 30% what should be the increase in the price of the box so that his profit of percentage remains the same

Answer 1

Given, SP1 = Rs 168
           Profit = 20%
 Hence, SP1 is 120% of CP1
=>168 = $\frac{120}{100}$×CP1
=>CP1 = 168×5/6
            =28×5 = 140
Now, cost of production is increased by 30%
So, new cp, CP2 = 140×$\frac{130}{100}$
                            = 14×13 = 182
As per question, new profit percentage should be same as previous .
Hence new SP, SP2 = CP2 ×120%
                                 = 182 ×$\frac{120}{100}$
                                 = 182 ×1.2 = 218.4

Increase in price of box = SP2-SP1
                                      = 218.4 -168
                                      = 50.4
 Ans : Rs 50.40          

Answer 2

Let the CP be ₹x
SP=₹168
Profit=20% of CP
=20x/100
We know that SP=CP+Profit
168=X+20x/100
168=120x/100
168×100/120=x
140=X

So, the CP=₹140
Profit=20/100×140=₹28

If CP is increased by 30%

=140+(140×30/100)
=₹182

ATQ:-
The profit should remain the same.

SP=CP×(100+G%/100)
182×(100+20/100)
218.4

This is SP

So increase in price of box=218.4-168

=₹50.4

This is the answer!