Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 10 - Geometry - 10.2 Triangles - Exercise Set 10.2 - Page 630: 62

Answer

The dimensions of Carpet: are Length is\[12\text{ m}\], Diagonal is \[13\text{ m}\] and the Breadth is\[5\text{ m}\].

Work Step by Step

It is given that the breadth of a rectangular carpet is 7 m less than its length and the diagonal is 1 m more than its length. Let length of rectangular carpet be\[l\]. Therefore, its breadth is \[\left( l-7 \right)\]m and diagonal be \[\left( l+1 \right)\]m. In rectangle ABCD, AC is the diagonal, AB and CD are the lengths and AD and BC are the breadths. \[\Delta ABC\]is a right triangle right angled at angle B as ABCD is rectangle. Therefore, all the angles intersect each other at right angle. Compute value of l by using Pythagorean Theorem in \[\Delta ABC\] and substitute the value of a and b into\[{{c}^{2}}={{a}^{2}}+{{b}^{2}}\]. \[\begin{align} & {{c}^{2}}={{a}^{2}}+{{b}^{2}} \\ & A{{C}^{2}}=A{{B}^{2}}+B{{C}^{2}} \\ & {{\left( l+1 \right)}^{2}}={{\left( l \right)}^{2}}+{{\left( l-7 \right)}^{2}} \\ & {{l}^{2}}+2l+1={{l}^{2}}+{{l}^{2}}-14l+49 \end{align}\] Re arranging the equation as follows: \[\begin{align} & 2l+1={{l}^{2}}-14l+49 \\ & 0={{l}^{2}}-14l+49-2l-1 \\ & 0={{l}^{2}}-16l+48 \\ & 0={{l}^{2}}-12l-4l+48 \end{align}\] Solving further the equation as follows; \[\begin{align} & 0=l\left( l-12 \right)-4\left( l-12 \right) \\ & 0=\left( l-4 \right)\left( l-12 \right) \\ & l=4,12 \end{align}\] Hence, the value of l is\[12\]. Compute the value of diagonal and breadth as shown below: \[\begin{align} & \text{Diagonal}=\left( l+1 \right) \\ & =12\text{ m}+1\text{ m} \\ & =13\text{ m} \end{align}\]. \[\begin{align} & \text{Breadth}=\left( l-7 \right) \\ & =12\text{ m}-7\text{ m} \\ & =5\text{ m} \end{align}\] Hence, the dimensions of Carpet are Length is\[12\text{ m}\], Diagonal is \[13\text{ m}\] and the Breadth is\[5\text{ m}\].
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