Question

What is the length of the diagonal of a rectangle having dimensions 20cm and 15 cm ? A) 10 cm B) 18 cm C) 25 cm D) 32 cm

Answer 1

Option (C) 25cm.

Given :-

• [] ABCD is a rectangle.
• In ΔBCD, m∠BCD = 90° , BC = 20cm and DC = 15cm.

To Find :-

• The length of diagonal.

Solution :-

In ΔBCD, m∠BCD = 90°

BD² = BC² + CD² (Pythagoras theorem)

=> BD² = 20² + 15²

=> BD² = 400 + 225

=> BD² = 625

=> BD = √625

=> BD = 25cm.

Hence,

• The length of diagonal is 25cm.

Answer 2

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✤ Required Answer:

✒GiveN:

• Dimension of the rectangle = 20 cm × 15 cm

✒To FinD:

• Diagonal of the rectangle.....?

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✤ How to solve?

The length, breadth and the diagonal of the rectangle forms a right angled triangle. And, we can solve to find the diagonal by using pythagoras theoram(@here) i.e.

$\large{ \cdot{ \boxed{ \rm{ {l}^{2} + {b}^{2} = {d}^{2} }}}}$

Here,

• l = length
• b = breadth
• d = diagonal

❄So, let's solve this question.....

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✤ Solution:

We have,

• Dimension of Rectangle = 20 cm × 15 cm

[Here, Dimension means the length and breadth collectively, and in most of the cases the longer side is considered as the length of the rectangle]

So, By using pythagoras theoram,

➝ l² + b² = d²➝ 20² + 15² = d²

➝ d = √20² + 15² cm

➝ d = √400 + 225 cm

➝ d = √625 cm

➝ d = 25 cm

❒ Diagonal of the rectangle = 25 cm (Option C)

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