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Mensuration (Class VIII)

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If the ratio of the areas of two squares is 9 : 25 and the sum of their areas is 306 sq. metres, then find the difference between their sides.

  1. 2 m

  2. 6 m

  3. 7 m

  4. 5 m

  5. None of these


Correct Option: B
Explanation:

Let area of the 1st square = 9x sq.m and area of the 2nd square = 25x sq.m. So, 9x + 25x = 306 x = 9 Then area of the 1st square = 81 sq.metres Area of the 2nd square = 225 sq.metres So, side of the first square = 9 m and second square = 15 m. Now, differences between sides = 15 - 9 = 6.

The length of a square is 5 cm. If the area of the square is equal to the difference of length and breadth of a rectangle, and the perimeter of the rectangle is 30 cm, then find the area of rectangle.

  1. 80 cm2

  2. 70 cm2

  3. 90 cm2

  4. 100 cm2

  5. None of these


Correct Option: D
Explanation:

It is given that,

Side of square = 5 cm and let the length of rectangle = l cm and breadth of rectangle = b cm.  So, l - b = area of square, = l - b = (5)2,

= l - b = 25 ---------------------(1) and,

Perimeter of rectangle = 30 cm, = 2(l + b) = 30,

= l + b = 15 --------------------(2),

After solving equation (1) and (2), we get

l = 20 cm and b = 5 cm,

So, area of rectangle = 20*5 = 100 cm2

Find the number of revolutions a wheel of diameter 28 cm makes in travelling a distance of 352 m.

  1. 200

  2. 176

  3. 154

  4. 182

  5. None of these


Correct Option: A
Explanation:

It is given that: Diameter of the wheel = 28 cm, so radius = 28/2 = 14 cm. Now, circumference of wheel = 2*pie*r = (2*22*14)/7 = 176 cm. Number of revolutions in 352 m = 352*100/176 = 200

The length of a rectangle is thrice its breadth. If its length is increased by 4 cm and the breadth is decreased by 3 cm, the area of the rectangle is decreased by 77 cm2. Therefore, the length of the rectangle is

  1. 20 cm

  2. 30 cm

  3. 39 cm

  4. 40 cm

  5. 24 cm


Correct Option: C
Explanation:

Let breadth =x cm and length = 3x cm Then, original area = x*3x = 3x2 cm2, After changing into dimensions, Area = (3x + 4)*(x – 3) = 3x2 – 5x - 12 So, 3x2 – (3x2 – 5x – 12) = 77, 5x + 12 = 77 x = 13, Length = 3*13 = 39 cm.

A circular wire with circumference 60 cm is cut and bent in the form of a rectangle whose sides are in the ratio of 8 : 7. Find the area of rectangle.

  1. 250 cm2

  2. 225 cm2

  3. 224 cm2

  4. 230 cm2

  5. None of these


Correct Option: C
Explanation:

Let the length of rectangle = 8x cm and breadth = 7x cm. Perimeter of rectangle = circumference of circle = 2(8x + 7x) = 60 x = 2 Then, length = 16 cm and breadth = 14 cm. Now, area of the rectangle = 224 cm2.

The breadth of a rectangular field is 4/5th of its length. If the perimeter of the field is 270 m, then what is 50% of the area of the field?

  1. 4500 m2

  2. 2500 m2

  3. 2250 m2

  4. 3500 m2

  5. None of these


Correct Option: C
Explanation:

Let length = x metres, then breadth = 4x/5 metres.

Perimeter = 270 metres

=> 2[x + 4x/5] = 270

=> x = 75 m

Length = 75 m and breadth = 4/5*250 = 60 m

Area = 75*60 = 4500 m2,

50% of area = 4500*50/100 = 2250 m2

A sector of 60 degrees of a circle has an area of 154/6 sq. cm. Find the radius of the circle.

  1. 4 cm

  2. 6 cm

  3. 5 cm

  4. 7 cm

  5. 14 cm


Correct Option: D
Explanation:

The sector has taken out from a circle. Therefore, radii of both will be same. So, area of sector = (pie*r2*angle)/360 degree = 154/6 = (22*r2*60)/7*360 = 154/6 r = 7 cm Therefore, radius of circle = 7 cm.  

Some soldiers are standing around a rectangular ground of dimensions 130 metres by 90 metres. The distance among each soldier is 11 meters. How much soldiers are standing around the ground?

  1. 50

  2. 40

  3. 20

  4. 30

  5. 60


Correct Option: B
Explanation:

Perimeter of ground = 2(130 + 90) = 440 m Because the distance among each soldier is 11 meters, so the number of soldiers = 440/11 = 40.

A painter uses a sheet measuring 30 cm by 40 cm lengthwise. If a margin of 5 cm is left on all four sides, then find the area of the margin.

  1. 500 cm2

  2. 700 cm2

  3. 600 cm2

  4. 400 cm2

  5. 300 cm2


Correct Option: C
Explanation:

Total are of the sheet = 40*30 = 1200 cm2  Length of sheet without margin = 40 - 5 - 5 = 30 cm Breadth of sheet without margin = 30 - 5 - 5 = 20 cm Area of sheet without margin = 30*20 = 600 cm2 Now, area of margin = 1200 - 600 = 600 cm2.

A horse is tightened on the corner of a square field. Find the length of a rope by which a horse must be tethered in order that it is able to graze an area of 693/2 sq. metres.

  1. 15 m

  2. 16 m

  3. 14 m

  4. 21 m

  5. None of these


Correct Option: D
Explanation:

The horse is tightened on a corner of a square field. Therefore, angle = 90 degrees. Because, (pie x r x r x 90 degree) = 693/2, = (22 x r2 x 90)/7 x 360 = 693/2, r = 21. So, length of the rope is 21 m.

The base of a parallelogram is four times its height. If the area of the parallelogram is 169 sq. cm, find its base.

  1. 26 cm

  2. 27 cm

  3. 28 cm

  4. 29 cm

  5. None of these


Correct Option: A
Explanation:

Let height = x cm. Then, base = 4x cm Now, area = 169 sq. cm b x h = 169, 4x * x = 169, x = 6.5 So, height = 6.5 cm, then base = 4*6.5 = 26 cm.

A rectangular field with length 70 m is to be fenced on three sides leaving a length of 10 m for entering in the field. If the area of the field is 3150 sq. m, how many metres of fencing will be required?

  1. 210 m

  2. 220 m

  3. 200 m

  4. 215 m

  5. None of these


Correct Option: B
Explanation:

It is given that length = 70 m. Then, breadth = area/length Breadth = 3150/70 = 45 m Now, perimeter of the rectangle = 2(70 + 45) = 230 m So, the quantity of fencing that will be required = 230 - 10 = 220 m.

A man took 20 seconds to cross a rectangular field diagonally, walking at the rate of 54 m/min, and another took the same time to cross the same field along its sides, walking at the rate of 63 m/min. The area of the field is

  1. 58.5 m2

  2. 60 m2

  3. 78.5 m2

  4. 80 m2

  5. None of these


Correct Option: A
Explanation:

Let the length = l m and breadth = b m.

So, the length of diagonal = 54*20/60 = 18 m,

Then, l2 + b2 = 182,

l2 + b2 = 324 ----------------------------------(1)

Total distance covered with the rate 63 m/min along with its sides = 

l + b = 63*20/60 = 21,

l + b = 21

On squaring both sides,

l2 + b2 + 2lb = 441 ---------------------------(2),

On solving equation 1 and 2,

2lb = 117

lb = 58.5

So, area of the field = 58.5 m2.

In measuring the sides of a rectangle, it is found that the length is 4% in excess and the breadth is 3% in deficit. Find the error percentage in the area.

  1. 0.88% increase

  2. 0.55% increase

  3. 0.99% increase

  4. 0.89% increase

  5. None of these


Correct Option: A
Explanation:

Let the length of rectangle = 10 and breadth = 10, then area = 10 x 10 = 100. Now, if 4% in excess in length and 3% in deficit in breadth, then area = 10.4 x 9.7 = 100.88. Increase in area = 100.88 - 100 = 0.88 Now, percentage error = 0.88%

A hall 25 m long and 20 m broad is surrounded by a veranda of uniform width of 5 m. The cost of flooring the veranda at the rate of Rs. 9.50 per sq. metre is

  1. Rs. 2375

  2. Rs. 2325

  3. Rs. 2350

  4. Rs. 2500

  5. None of these


Correct Option: A
Explanation:

 Area of hall = 25*20 = 500 sq. metres Length of hall with veranda = 25 + 5 = 30 m Breadth of hall with veranda = 20 + 5 = 25 m Area of hall with veranda = 30*25 = 750 sq. metres Then, area of veranda = 750 - 500 = 250 sq. metres Cost of flooring = 250*9.50 = Rs. 2375

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