57
Q:

If the radius of a circle is decreased by 50%, find the percentage decrease in its area.

A) 55% B) 65%
C) 75% D) 85%

Answer:   C) 75%



Explanation:

Let original radius = R.

New radius = 

Original area =  and new area = 

Decrease in area =  = 75%

Q:

The area of a square is equal to the area of a rectangle. The length of the rectangle is 5 cm more than a side of the square and its breadth is 3 cm less than the side of the square. What is the perimeter of the rectangle ? 

A) 15 cm B) 18 cm
C) 34 cm D) 26 cm
 
Answer & Explanation Answer: C) 34 cm

Explanation:

Let the side of the square be 's' cm

length of rectangle = (s+5) cm

breadth of rectangle = (s-3)cm

(s+5) (s-3) =

 - 5s - 3s - 15 = 

2s = 15

Perimeter of rectangle = 2(L+B) = 2(s+5 + s–3) = 2(2s + 2)

= 2(15 + 2) = 34 cm 

Report Error

View Answer Workspace Report Error Discuss

8 322
Q:

Area of a square and a rectangle are equal. If side of the square is 40 cm and length of the rectangle is 64 cm, what is the perimeter of the rectangle ?

A) 187 cm B) 178 cm
C) 149 cm D) 194 cm
 
Answer & Explanation Answer: B) 178 cm

Explanation:

Area of square = 40 x 40

= 1600 sq.cm

Given that the areas of Square and Rectangle are equal

=> Area of rectangle = 1600 Sq.cm

We know that, Area of rectangle = L x B

Given L = 64 cm

Breadth of rectangle = 1600/64 = 25 cm

Perimeter of the rectangle = 2(L + B) = 2(64+25) = 178 cm.

Report Error

View Answer Workspace Report Error Discuss

15 389
Q:

The question given below contain two statements giving certain data. You have to decide whether the data given in the statements are sufficient for answering the question ?

Question :

What is the height of a right-angled triangle ?

Statements :

A. The area of the triangle is 20 times its base.

B. The perimeter of the triangle is equal to that of a square of the side 10 cm.

A) Only statement A is required B) Only statement B is required
C) Both A & B are required D) Neither (A) nor (B) is reuired
 
Answer & Explanation Answer: A) Only statement A is required

Explanation:

From statement (A),

20b = (1/2) × b × h

h = 40 cm.

Report Error

View Answer Workspace Report Error Discuss

13 306
Q:

The length, breadth and height of a room are in the ratio 7:3:1. If the breadth and height are doubled while the length is halved, then by what percent the total area of the 4 walls of the room will be increased  ?

A) 90% B) 88%
C) 85% D) 84%
 
Answer & Explanation Answer: A) 90%

Explanation:

Let length, breadth and height of the room be 7, 3, 1 unit respectively.

Area of walls = 2(l+b)xh = 2(7+3)x1 = 20 sq. unit.

Now, length, breadth and height of room will become 3.5, 6 and 2 respectively. 

Area of walls = 2(l+b)xh = 2(3.5+6)x2 = 38 sq. unit. 

% Increase in the area of walls = (38-20)x100/20 = 90%.

Report Error

View Answer Workspace Report Error Discuss

11 404
Q:

The difference between circumference and semidiameter of a circle is 37 cm. What is the diameter of the circle ?

A) 18 cm B) 12 cm
C) 16 cm D) 14 cm
 
Answer & Explanation Answer: D) 14 cm

Explanation:

circumference of a circle = 2r

=> 2 × 22/7 × r – r = 37

=> 37/7 × r = 37

=> r = 7 cm.

Diameter D = 2r = 7×2 = 14 cm.

Report Error

View Answer Workspace Report Error Discuss

15 522