All questions of Mensuration for Computer Science Engineering (CSE) Exam

A circular wire of radius 56 cm is cut and bent in the form of a rectangle whose sides are in the ratio of 6:5. The smaller side of the rectangle is
  • a)
    70cm
  • b)
    75cm
  • c)
    80cm
  • d)
    85cm
  • e)
    None of these
Correct answer is option 'C'. Can you explain this answer?

Preeti Khanna answered
The perimeter of the circle, that is, the rectangle is,
P=2πr = 2 * 22/7 * 56 =16×22 cm.
Let us assume the actual length and breadth of the rectangle be, 6xand 5x
So perimeter will be,
P=2(6x+5x)=22x
16×22=22x
X=16.
The smaller side or breadth =5x=80cm

A well with 28 m inside diameter is dug out 18 m deep. The earth taken out of it has been evenly spread all around it to a width of 21 m to form an embarkment. Find the height of the embarkment.
  • a)
    3 m
  • b)
    8 m
  • c)
    9 m
  • d)
    6 m
  • e)
    None of these
Correct answer is option 'A'. Can you explain this answer?

Aarav Sharma answered
Solution:

Given:
Diameter of the well = 28 m
Depth of the well = 18 m
Width of the embankment = 21 m

We need to find the height of the embankment.

Step 1: Calculate the radius of the well
The diameter of the well is 28 m, so the radius will be half of the diameter.
Radius = 28 m / 2 = 14 m

Step 2: Calculate the volume of the well
The volume of a cylinder is given by the formula: V = πr²h, where r is the radius and h is the height.
In this case, the height of the well is 18 m.
Volume of the well = π * (14 m)² * 18 m
Volume of the well = 3528π m³

Step 3: Calculate the volume of the embankment
The embankment is formed by spreading the earth taken out of the well in a circular shape around it.
The width of the embankment is 21 m, so the outer radius of the embankment will be the sum of the radius of the well and the width of the embankment.
Outer radius = 14 m + 21 m = 35 m

The volume of the embankment can be calculated by subtracting the volume of the well from the volume of the embankment.
Volume of the embankment = π * (35 m)² * h_embankment

Since the earth taken out of the well is evenly spread around the embankment, the volume of the embankment will be equal to the volume of the well.
So, we can write the equation as:
Volume of the embankment = Volume of the well
π * (35 m)² * h_embankment = 3528π m³

Step 4: Calculate the height of the embankment
Canceling out π on both sides of the equation and simplifying, we get:
(35 m)² * h_embankment = 3528 m³
h_embankment = 3528 m³ / (35 m)²
h_embankment = 3528 m³ / 1225 m²
h_embankment = 2.88 m

Therefore, the height of the embankment is approximately 2.88 m, which is approximately 3 m.

Hence, the correct answer is option A) 3 m.

Circumference of a circle A is 22/7 times perimeter of a square. Area of the square is 441 cm². What is the area of another circle B whose diameter is half the radius of the circle A(in cm²)?
  • a)
    354.5
  • b)
    346.5
  • c)
    316.5
  • d)
    312.5
  • e)
    None of the Above
Correct answer is option 'B'. Can you explain this answer?

Anshul Singh answered
Area of square=441 cm2
i.e. (side)2=441 cm2
side=21cm

Circumference of circle A=2πr
Perimeter of square(p)=4*side=(4*21)cm=84cm

According to question,
Circumference of A=22/7 of p
i.e. 2πr=(22/7)*84
2(22/7)*r=(22/7)*84
2r=84
r=42cm

let radius of B be 'R',
Diameter of B=(1/2) of radius of A
Diameter of B=(1/2)*42=21cm
R=(21/2)cm

Area of Circle B=πR2
=(22/7)*(21/2)*(21/2)cm2
hence on calculating the above solution we
get that area of circle B=346.5
i.e. option b).
thanking you if you understand it so plzzz follow me.

If each side pair of opposite sides of a square is increased by 20 m, the ratio of the length and breadth of the rectangular so formed becomes 5:3. The area of the old square is?
  • a)
    990m²
  • b)
    900m²
  • c)
    930m²
  • d)
    945m²
  • e)
    None of the Above
Correct answer is option 'B'. Can you explain this answer?

Ankur Mathur answered
Let the side of squares be x sq unit.
therefore as a pair opposite side increased by 20 units, hence now the rectangle obtained is of dimension-:
x, (x+20)

also the ration of sides is 5:3
so,
(x+20/x)= 5/3

solving this you will get X=30

hence the dimension of the square was of 30*30
hence area was 900sq unit.

The length of a plot is four times its breath. A playground measuring 400 square meters occupies one fourth of the total area of a plot. What is the length of the plot in meter.?
  • a)
    20
  • b)
    30
  • c)
    60
  • d)
    40
  • e)
    80
Correct answer is option 'E'. Can you explain this answer?

Aarav Sharma answered
To solve this problem, we need to use the given information to find the length of the plot. Let's break down the information step by step:

1. The length of a plot is four times its breadth: Let's assume the breadth of the plot is 'x'. According to the given information, the length of the plot would be 4x.

2. A playground occupies one fourth of the total area of the plot: The area of the playground is given as 400 square meters. Since the playground occupies one fourth of the total area of the plot, we can calculate the total area of the plot by multiplying the area of the playground by 4. So, the total area of the plot would be 400 * 4 = 1600 square meters.

3. Now, we can use the total area of the plot to find the length. The formula to calculate the area of a rectangle is length * breadth. We know that the area of the plot is 1600 square meters and the length is 4x. Substituting these values into the formula, we get:

4x * x = 1600

4. Simplifying the equation, we have:

4x^2 = 1600

5. Dividing both sides of the equation by 4, we get:

x^2 = 400

6. Taking the square root of both sides, we get:

x = √400

7. Simplifying the square root, we have:

x = 20

8. Since the length of the plot is four times its breadth, we have:

Length = 4x = 4 * 20 = 80 meters

Therefore, the length of the plot is 80 meters. The correct answer is option E.

A rectangular ground 16m long and 10m breadth. It has a gravel path 2.5m wide all around it on the outside. What is the area of the path?
  • a)
    159 m²
  • b)
    155 m²
  • c)
    187 m²
  • d)
    183 m²
  • e)
    None of the Above
Correct answer is option 'B'. Can you explain this answer?

Sagar Sharma answered
To find the area of the path, we need to subtract the area of the inner rectangle (without the path) from the area of the outer rectangle (with the path).

The area of the outer rectangle is given by the length multiplied by the breadth:
Area of outer rectangle = 16m * 10m = 160m²

The area of the inner rectangle is the length and breadth reduced by twice the width of the path on each side:
Length of inner rectangle = 16m - 2(2.5m) = 16m - 5m = 11m
Breadth of inner rectangle = 10m - 2(2.5m) = 10m - 5m = 5m

Area of inner rectangle = 11m * 5m = 55m²

Therefore, the area of the path is:
Area of path = Area of outer rectangle - Area of inner rectangle
Area of path = 160m² - 55m²
Area of path = 105m²

So the area of the path is 105 square meters.

In a rectangle the ratio of the length and breadth is 3:2. If each of the length and breadth is increased by 4m their ratio becomes 10:7. The area of the original rectangle in m² is?
  • a)
    384
  • b)
    486
  • c)
    546
  • d)
    864
  • e)
    None of the Above
Correct answer is option 'D'. Can you explain this answer?

Sagar Sharma answered
Understanding the Problem
To find the area of the original rectangle, we start by acknowledging the given ratios and conditions.
Step 1: Define Variables
- Let the length of the rectangle be 3x and the breadth be 2x, based on the ratio of 3:2.
Step 2: Set Up the Equation
- According to the problem, when both length and breadth are increased by 4m, the new ratio becomes 10:7.
- This can be expressed as:
(3x + 4) / (2x + 4) = 10 / 7
Step 3: Cross-Multiply and Simplify
- Cross-multiplying gives:
7(3x + 4) = 10(2x + 4)
- Expanding both sides results in:
21x + 28 = 20x + 40
Step 4: Solve for x
- Rearranging yields:
21x - 20x = 40 - 28
x = 12
Step 5: Calculate Length and Breadth
- Plugging x back into our expressions:
Length = 3x = 36m
Breadth = 2x = 24m
Step 6: Find the Area
- The area of the rectangle is calculated as:
Area = Length × Breadth = 36m × 24m = 864m²
Conclusion
The area of the original rectangle is 864m², confirming that the correct answer is option 'D'.

The length of a wall is 5/4 times of its height. If the area of wall will be 500m². What is the sum of the length and height of the wall?
  • a)
    55m
  • b)
    45m
  • c)
    40m
  • d)
    50m
  • e)
    None of these
Correct answer is option 'B'. Can you explain this answer?

Sagar Sharma answered
Let's assume the height of the wall is "h".
The length of the wall will be 5/4 times the height, which is (5/4)h.

The area of the wall is calculated by multiplying the length and height:
Area = Length × Height
500 = (5/4)h × h

To solve for h, we can multiply both sides of the equation by 4/5:
(4/5) × 500 = (4/5) × (5/4)h × h
400 = h^2

Taking the square root of both sides, we find:
h = √400
h = 20

Therefore, the height of the wall is 20m.

The length of the wall can be found by multiplying the height by 5/4:
Length = (5/4) × 20
Length = 25

So, the length of the wall is 25m.

The radius of a circle is 4 m. What is the radius of another circle whose area is 16 times of that first?
  • a)
    16 m
  • b)
    64 m
  • c)
    256 m
  • d)
    400 m
  • e)
    None of these
Correct answer is option 'A'. Can you explain this answer?

Aarav Sharma answered
Given:
The radius of the first circle is 4 m.

To find:
The radius of another circle whose area is 16 times that of the first circle.

Solution:
Let's assume the radius of the second circle is r.

Step 1: Calculate the area of the first circle.
The formula for the area of a circle is A = πr².
Substituting the given radius value into the formula:
A1 = π(4²)
A1 = 16π

Step 2: Calculate the area of the second circle.
The area of the second circle is given as 16 times the area of the first circle.
So, A2 = 16 * A1
A2 = 16 * 16π
A2 = 256π

Step 3: Find the radius of the second circle.
The formula for the area of a circle is A = πr².
Substituting the area of the second circle into the formula:
256π = πr²

Step 4: Solve for r.
Dividing both sides of the equation by π:
256 = r²

Taking the square root of both sides:
r = √256
r = 16

Conclusion:
The radius of the second circle is 16 m, which corresponds to option A.

The length of a park is four times of its breadth. A playground whose area is 1600 m² covers 1/4th part of the park. The length of the park is?
  • a)
    108 m
  • b)
    140 m
  • c)
    120 m
  • d)
    160 m
  • e)
    180 m
Correct answer is option 'D'. Can you explain this answer?

Sagar Sharma answered
The area of a rectangle is given by the formula A = length * breadth.

Let's assume the breadth of the park is x meters.
According to the problem, the length of the park is four times its breadth, so the length is 4x meters.

The area of the park is given as 1600 square meters, so we can write the equation:
1600 = 4x * x

Simplifying the equation:
1600 = 4x^2

Dividing both sides by 4:
400 = x^2

Taking the square root of both sides:
x = ±20

Since the breadth cannot be negative, we take the positive value:
x = 20 meters

Therefore, the breadth of the park is 20 meters and the length is 4 times the breadth, which is 4*20 = 80 meters.

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