If the Same Number Be Added to the Numbers 5, 11, 15 and 31, the Resulting Numbers Are in Proportion. Find the Number. - Mathematics

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Sum

If the same number be added to the numbers 5, 11, 15 and 31, the resulting numbers are in proportion. Find the number.

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Solution

Let x be added to each number, then the numbers will be 5 + x, 11 + x, 15 + x and 31 + x

According to the condition

`(5 + x)/(11 + x) = (15 + x)/(31 + x)`

By cross multiplication,

(5 + x)(31 + x) = (15 + x)(11 + x)

⇒ 155 + 5x + 31x + x2 = 165 + 11x + 15x + x2

⇒ 155 + 36x + x2 = 165 + 26x + x2

⇒ 36x + x2 - 26x - x2 = 165 - 155

⇒ 10x = 10 ⇒ x = `10/10 = 1`

1 should be added

Concept: Solving Linear Inequations
  Is there an error in this question or solution?
Chapter 14: Linear Equations in one Variable - Exercise 14 (B) [Page 169]

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Selina Concise Mathematics Class 8 ICSE
Chapter 14 Linear Equations in one Variable
Exercise 14 (B) | Q 19 | Page 169
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