Question

The price of 7 notebooks and 3 textbooks is 245/-. But the price of 3 notebooks and 5 textbooks
is 235/-. Find the cost of 2 notebooks and 2 textbooks.​

Answer 1

Answer:

The cost of 2 notebooks and 2 textbooks is 110/-

Step-by-step explanation:

Given :

• The price of 7 notebooks and 3 textbooks is 245/-

• The price of 3 notebooks and 5 textbooks  is 235/-

To find :

the cost of 2 notebooks and 2 textbooks

Solution :

Let the cost of 1 notebook be x and the cost of 1 textbook be y.

• The price of 7 notebooks and 3 textbooks is 245/-

Cost of 7 notebooks = 7x

Cost of 3 textbooks = 3y

 7x + 3y = 245 ➙ [1]

• The price of 3 notebooks and 5 textbooks is 235/-

Cost of 3 notebooks = 3x

Cost of 5 textbooks = 5y

  3x + 5y = 235 ➙ [2]    

Multiplying equation [1] by 5 and equation [2] by 3, we get

35x + 15y = 1225 ➙ [3]

9x + 15y = 705 ➙[4]

Subtract equation [4] from equation [3],

35x + 15y - (9x + 15y) = 1225 - 705

35x + 15y - 9x - 15y = 520

   35x - 9x = 520

    26x = 520

     x = 520/26

     x = 20

∴ Price of 1 notebook = 20/-

Substitute x = 20 in equation [2],

3x + 5y = 235

3(20) + 5y = 235

60 + 5y = 235

  5y = 235 - 60

  5y = 175

   y = 175/5

   y = 35

∴ Cost of 1 textbook = 35/-

The cost of 2 notebooks and 2 textbooks :

➛ 2x + 2y

➛ 2(20) + 2(35)

➛ 40 + 70

➛ 110

∴ The cost of 2 notebooks and 2 textbooks is 110/-