1. The length of a rectangle is two - fifths of the radius of a circle. The radius of the circle is equal to the side of the square, whose area is 1225 sq.units. What is the area (in sq.units) of the rectangle if the rectangle if the breadth is 10 units?
A. 140
B. 156
C. 175
D. 214
E. None of these
Answer: Option A
Explanation:
Given that the area of the square = 1225 sq.units
=> Side of square = √1225 = 35 units
The radius of the circle = side of the square = 35 units Length of the rectangle = [latex]\frac{2}{5}[/latex] × 35 = 14 units
Given that breadth = 10 units
Area of the rectangle = lb = 14 × 10 = 140 sq.units
2. The sector of a circle has radius of 21 cm and central angle 135o. Find its perimeter?
A. 91.5 cm
B. 93.5 cm
C. 94.5 cm
D. 92.5 cm
E. None of these
Answer: Option A
Explanation:
Perimeter of the sector = length of the arc + 2(radius)
= ([latex]\frac{135}{360}[/latex] × 2 × [latex]\frac{22}{7}[/latex] × 21) + 2(21)
= 49.5 + 42 = 91.5 cm
3. An order was placed for the supply of a carper whose length and breadth were in the ratio of 3 : 2. Subsequently, the dimensions of the carpet were altered such that its length and breadth were in the ratio 7 : 3 but were was no change in its parameter. Find the ratio of the areas of the carpets in both the cases.
A. 4 : 3
B. 8 : 7
C. 4 : 1
D. 6 : 5
E. None of these
Answer: Option B
Explanation:
Let the length and breadth of the carpet in the first case be 3x units and 2x units respectively.
Let the dimensions of the carpet in the second case be 7y, 3y units respectively.
From the data,.
2(3x + 2x) = 2(7y + 3y)
=> 5x = 10y
=> x = 2y
Required ratio of the areas of the carpet in both the cases
= 3x × 2x : 7y × 3y
= 6[latex]{x}^{2}[/latex] : 21[latex]{y}^{2}[/latex]
= 6 × [latex]{(2y)}^{2}[/latex] : 21y2
= 6 × 4[latex]{y}^{2}[/latex] : 21[latex]{y}^{2}[/latex]
= 8 : 7
4. A wire when bent in the form of a square encloses an area of 484 sq.cm. What will be the enclosed area when the same wire is bent into the form of a circle? (Take π=227)
A. 462 [latex]{cm}^{2}[/latex]
B. 539 [latex]{cm}^{2}[/latex]
C. 616 [latex]{cm}^{2}[/latex]
D. 693 [latex]{cm}^{2}[/latex]
Answer: Option C
Explanation:
Area of a square = side × side
The perimeter of a square = 4 × side
Given, wire, when bent in the form of a square, encloses an area of 484 sq.cm
Side = √484 = 22 cm
Perimeter = 88 cm
Same wire is used to make a circle.
The perimeter of a circle of radius r = 2πr
⇒ 2πr = 88
⇒ [latex]\frac{44r}{7}[/latex] = 88
⇒ r = 14 cm
Area of a circle of radius r = π[latex]{r}^{2}[/latex]
Area enclosed by the circle = 227 × 142
⇒ Area enclosed by the circle = 616 [latex]{cm}^{2}[/latex]
5. A square of side 22 cm is made from a single wire. The same wire is then bent to form a circle. The area of the circle formed is (π = 22/7)
A. 416 [latex]{cm}^{2}[/latex]
B. 343 [latex]{cm}^{2}[/latex]
C. 528 [latex]{cm}^{2}[/latex]
D. 616 [latex]{cm}^{2}[/latex]
Answer: Option D
Explanation:
Perimeter of a square = 4 × side
Given, side of the square = 22 cm
∴ The perimeter of the square = 88 cm
Now, the same wire is used to form a circle.
∴ The circumference of the circle formed = perimeter of the square
Circumference of a circle = 2πr
⇒ 2πr = 88
⇒ r = [latex]\frac{44}{π}[/latex] = 14 cm
Area of a circle = π[latex]{r}^{2}[/latex]
⇒ Area of the circle formed =227 × 142 = 616 [latex]{cm}^{2}[/latex]