Math Problem Statement

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The following figure shows the emblem. A semicircular part has been removed from the rectangular metal sheet which is 20 cm in length and 14 cm in breadth, and the removed part has been attached to the other side of a rectangle. (i) Find the value of h. (ii) Calculate the area of the semicircular part removed from the metal sheet (Area of a circle is πr²). (iii) Find the area of a shaded region.

Solution

To solve the problem presented in the image, let's break down each part of the question and solve it step by step. The problem involves a rectangular metal sheet with a semicircular part removed. The sheet dimensions are given as 20 cm by 14 cm, and the semicircular part has been cut from one end. Here are the steps we need to follow:

Part (i): Find the value of hh

We assume hh represents the height from the center of the semicircle's diameter to the farthest point on the rectangle. Given the radius of the semicircle:

  • The semicircle has a diameter of 14 cm (equal to the breadth of the rectangle), so the radius rr is: r=142=7cmr = \frac{14}{2} = 7 \, \text{cm}

The value of hh is equal to the radius rr of the semicircle. Thus: h=7cmh = 7 \, \text{cm}

Part (ii): Calculate the area of the semicircular part removed

The area AA of a semicircle is given by: A=12πr2A = \frac{1}{2} \pi r^2 Substitute r=7cmr = 7 \, \text{cm}: A=12π(7)2=12π×49=24.5π76.96cm2A = \frac{1}{2} \pi (7)^2 = \frac{1}{2} \pi \times 49 = 24.5 \pi \approx 76.96 \, \text{cm}^2

So, the area of the semicircular part removed is approximately 76.96cm276.96 \, \text{cm}^2.

Part (iii): Find the area of the shaded region

To find the area of the shaded region, we need to calculate the area of the original rectangular metal sheet and then subtract the area of the semicircular part that was removed.

  1. Area of the rectangle: Area of rectangle=length×breadth=20cm×14cm=280cm2\text{Area of rectangle} = \text{length} \times \text{breadth} = 20 \, \text{cm} \times 14 \, \text{cm} = 280 \, \text{cm}^2

  2. Subtract the area of the semicircle: [ \text{Shaded area} = \text{Area of rectangle} - \text{Area of semicircle} = 280 , \text{cm}^2 - 76.96 , \text{cm}^2

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Math Problem Analysis

Mathematical Concepts

Geometry
Area Calculation

Formulas

Area of semicircle = (1/2)πr²
Area of rectangle = length × breadth

Theorems

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Suitable Grade Level

Grades 7-9