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Question

The length of a diagonal in cm of a rectangle of length 9 cm and width 5 cm is

This question was previously asked in
RRB NTPC 2015 CBT 1 Question Paper (29-Mar-2016) (Shift 1)
The correct answer is
$\sqrt{106}$

Finding the Rectangle Diagonal Length

To find the length of the diagonal of a rectangle, we can use the Pythagorean theorem. The theorem states that in a right-angled triangle, the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides. In a rectangle, the length, width, and diagonal form a right-angled triangle.

Applying the Pythagorean Theorem

Let the length of the rectangle be '$l$' and the width be '$w$'. Let the diagonal be '$d$'. According to the Pythagorean theorem:

$d^2 = l^2 + w^2$

Calculating the Diagonal

Given:

  • Length, $l = 9$ cm
  • Width, $w = 5$ cm

Substitute the values into the formula:

$d^2 = 9^2 + 5^2$

$d^2 = 81 + 25$

$d^2 = 106$

To find the diagonal '$d$', take the square root of both sides:

$d = \sqrt{106}$

Since length must be a positive value, we only consider the positive square root.

Conclusion

The length of the diagonal is $\sqrt{106}$ cm.

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