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Mathematics

Form the pair of linear equations in the following problem, and find their solutions (if they exist) by the elimination method :

Meena went to a bank to withdraw ₹ 2000. She asked the cashier to give her ₹ 50 and ₹ 100 notes only. Meena got 25 notes in all. Find how many notes of ₹ 50 and ₹ 100 she received.

Linear Equations

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Answer

Let no. of ₹ 50 notes be x and no. of ₹ 100 notes be y.

Given,

Meena got 25 notes in all.

x + y = 25 ……..(1)

Given,

Total money = ₹ 2000

⇒ 50x + 100y = 2000

⇒ 50(x + 2y) = 2000

⇒ x + 2y = 200050\dfrac{2000}{50}

⇒ x + 2y = 40 ………(2)

Subtracting equation (1) from (2), we get :

⇒ x + 2y - (x + y) = 40 - 25

⇒ x - x + 2y - y = 15

⇒ y = 15.

Substituting value of y in equation (1), we get :

⇒ x + 15 = 25

⇒ x = 25 - 15 = 10.

Hence, pair of linear equations are x + 2y = 40, x + y = 25, where x and y are respectively the number of ₹50 and ₹100 notes; x = 10, y = 15.

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