On selling a book for rs 550 a boy gains 10 what should be the selling price if desired profit is 20

Question 7 Percentage Exercise 7.3

Answer:

(i) It is given that

C.P. = ₹ 650

Profit = 20%

We know that

S.P. = [1 + P/100] of C.P.

Substituting the values

= [1 + 20/100] × 650

By further calculation

= 120/100 × 650

So we get

= 12 × 65

= ₹ 780

Therefore, the selling price of the calculator is ₹ 780.

(ii) It is given that

S.P. = ₹ 780

Discount = 20%

We know that

S.P. = [1 – d/100] of M.P

Substituting the values

780 = [1 – 20/100] of M.P.

By further calculation

780 = 80/100 of M.P.

It can be written as

M.P. = 780 × 100/80

So we get

M.P. = 780 × 10/8

M.P. = 7800/8

M.P. = ₹ 975

Therefore, the market price of the calculator is ₹ 975.

Video transcript

hello everybody welcome to lido learning channel my name is rajna and we are going to solve this question a shopkeeper purchased a calculator for rupees 650 he sells it at a discount of 20 and still makes a profit of 20 find selling price so in this question it's shopkeeper purchased a calculator so that mean this is cost price so cost price of the item is rupees 650 and he made a discount so uh as well as a profit so profit is 20 so this 20 percent would be calculated of cost price so 20 upon 100 multiplied by cp that is 650 zeros are cancelled and 65 multiplied by 20 is 170 rupees so this is the profit now we have to find selling price selling price is profit plus cost price so profit is 170 cost price is 650 after adding we have rupees 780 so this is selling price now we also have to calculate marked price but we know selling price now so let's do this so we can let marked price as x because we know that marked price is always we know that discount is always calculated on marked price so that's why we have left it as x now discount is 20 so this would be 20 of marked price so 20 upon 100 of x after further calculation we have x upon 5 now this is the discount x upon five we have to find marked price so we know that marked price would be equal to or we can apply the formula of selling price selling price is marked price minus discount selling price now we know let's substitute the value 780 mark price is x discount is x upon 5 so after substituting and calculating we have 780 is equal to 5 in the denominator 5x minus x so we have 780 is equal to 4x upon 5 now 4 upon 5 can we transposed to the left hand side and we would have 5 at the numerator and 4 at the denominator is equal to x now we can simplify this so after this simplification we can divide 780 by 4 so it would we would get 900 195 that should be multiplied by 5 and we would have 975 so this 975 rupees is the value of x that means this is marked price so i hope you understand the method how did we calculate marked price and selling price see you in my next video don't forget to like share and subscribe the channel thank you for watching

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How to calculate selling price using cost and profit percent?

We know, Selling Price = Cost Price + Profit

Selling Price = Cost Price + $\frac{Profit Percentage}{100}$ × Cost Price

Selling Price = $\frac{100 × Cost Price + Profit Percentage × Cost Price}{100}$

Selling Price = Cost Price [$\frac{100 + Profit Percentage}{100}$]; [Here, cost price and profit% are known.]

1. Ryan bought a book for $100 and sold it at a profit of 10%. Find the selling price of the book.

Solution:

Given cost price of the book = $100

Profit% = 10%

We know, Selling Price = Cost Price [$\frac{100 + Profit Percentage}{100}$]

= 100 ($\frac{100 + 10}{100}$)