Data Interpretation - Pie Charts - Discussion

180*100/120 = 150.
150*25/100 = 37.5

Here 1st we need to find the cost price to find printing cost,
It is printing cost = (25*cp)/100.

We have formula for finding cp = (100*sp)/(100+gain%)
=(100*180)/(120)
=150

Therefore printing cost=(25*150)/100
=37.5

If the cost of paper is 20% of above it mean that = 100+20=120
So 120:25::180:x x=25*180/120=37.

Please anyone tell me that why the calculations are based on sp?

Can I use cp for calculation?

What if i try to solve the sum by taking c.p. as x? Will the process be lengthy?

Firstly, Read the question thoroughly. The question says that "The price of the book is marked 20% above CP(Cost Price) and the Marked price of the book is Rs 180. Marked Price is nothing but Sp(Selling price). These are the assumptions we can make from the question.

Soln: We need to find the CP now from the data given above.
Lets take the CP as 'x'. As the price of the book is marked(SP) 20% above the CP, the equation becomes:
x+20/100(x)=180
=> x=150
So, CP= Rs 150

Now, we need to find the cost of paper used in a single copy of the book.. i.e
25/100(150)=37.5

Can anyone still clearly explain me this?

Question says price is marked 20% above cost, Hence if cost was 100rs, the marked price will be Rs100 + 20% ie 120.

From were does 120 comes? plesse explain.

180 is the selling price of the book. It includes the cost price of the book as well as the profit made on the book which is 20% of the cost price of the book. Together they make 180.