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A sum of ₹ 500 is in the form of notes of denominations of ₹ 5 and ₹ 10. If the total number of notes is 90, find the number of notes of each type. - Mathematics

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Question

A sum of ₹ 500 is in the form of notes of denominations of ₹ 5 and ₹ 10. If the total number of notes is 90, find the number of notes of each type.

Sum

Solution

Let the number of ₹ 5 notes = x

∴ The number of ₹ 10 notes = 90 – x

Value of ₹ 10 notes = x × ₹ 5 = ₹ 5x

and value of ₹10 notes = (90 – x) × ₹ 10 = ₹(900 – 10x)

∴ Total value of all the notes = ₹ 500

∴ 5x + (90 – 10x) = 500

⇒ 5x + 900 – 10x = 500

⇒ -5x + 900 = 500

⇒ 900 – 500 = 5x

⇒ x = `400/5`

⇒ x = 80

∴ The number of ₹ 5 notes = x = 80

and the number of ₹ 10 notes = 90 – x

= 90 – 80 = 10

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Simple Linear Equations in One Variable
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Chapter 12: Simple Linear Equations (Including Word Problems) - Exercise 12 (D)

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Selina Concise Mathematics [English] Class 7 ICSE
Chapter 12 Simple Linear Equations (Including Word Problems)
Exercise 12 (D) | Q 20

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