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Question

What is the area in sq. cm. of the triangle with a base of 8 cm and sides of length 6 cm each?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is
$8\sqrt{5}$

Triangle Area Calculation

The problem asks for the area of a triangle with a base of 8 cm and two equal sides of 6 cm. This is an isosceles triangle.

Finding Triangle Height

To calculate the area of a triangle, we use the formula:

\(\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}\)

We know the base is 8 cm, but we need to find the height. We can find the height by dividing the isosceles triangle into two identical right-angled triangles. The height acts as one leg, half the base (4 cm) is the other leg, and one of the equal sides (6 cm) is the hypotenuse.

Using the Pythagorean theorem (\(a^2 + b^2 = c^2\)):

\(\text{height}^2 + (\frac{\text{base}}{2})^2 = \text{side}^2\)

\(h^2 + (4 \text{ cm})^2 = (6 \text{ cm})^2\)

\(h^2 + 16 \text{ cm}^2 = 36 \text{ cm}^2\)

\(h^2 = 36 \text{ cm}^2 - 16 \text{ cm}^2\)

\(h^2 = 20 \text{ cm}^2\)

\(h = \sqrt{20 \text{ cm}^2} = \sqrt{4 \times 5} \text{ cm} = 2\sqrt{5} \text{ cm}\)

Calculating Triangle Area

Now we can calculate the area using the base and the calculated height:

\(\text{Area} = \frac{1}{2} \times 8 \text{ cm} \times 2\sqrt{5} \text{ cm}\)

\(\text{Area} = 4 \text{ cm} \times 2\sqrt{5} \text{ cm}\)

\(\text{Area} = 8\sqrt{5} \text{ cm}^2\)

The area of the triangle is \(8\sqrt{5}\) sq. cm.

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Similar Questions

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  2. Calculate the length of the diagonal of a square if the area of the square is 32 cm\(^2\).
  3. A farmer wants to fence his rectangular field of length 200 m and area 3000 \(\text{m}^2\). If the cost of fencing per metre is 5 rupees, what is the total cost of fencing in rupees?
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  5. A car has two wipers which do not overlap. Each wiper has a blade of length 18 cm sweeping through an angle of \(126^\circ\). Find the total area cleaned at each sweep of the blades. Take \(\pi = 22/7\)
  6. \(ABCD\) is a diameter of a circle of radius 12 cm. The lengths \(AB\), \(BC\) and \(CD\) are equal. Semi-circles are drawn on \(AB\) and \(BD\) as diameters as shown in the given figure. Find area of the shaded region.

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Important Questions from 2-D Mensuration

  1. The length of a rectangular plot is $(x^2 + xy + y^2)$ m and its breadth is $(x^2 - 5xy - y^2)$ m.
    Find its perimeter, when $x = 1$ and $y = -1$.
  2. The ratio between the perimeter and breadth of a rectangle is 3: 1. If the area of the rectangle is $98 \text{ cm}^2$, find the perimeter (in cm) of the rectangle.
  3. The shorter side of a rectangle is 15 cm less than the longer side. The numerical value of its area is equal to 5 times the numerical value of its perimeter. What is the length (in cm) of its longer side?

  4. In a circle of radius 10.5 cm, if the angle of a sector is $\frac{2\pi}{3}$, then the perimeter of the sector is (in cm):
    (Take $\pi = \frac{22}{7}$)
  5. Find the circumference (in m) of the largest circle that can be inscribed in a rectangle whose dimensions are given as 114 m and 63 m.
    Take $\pi = \frac{22}{7}$
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