81. The area of the four walls of a hall is 660 sq. m, the length is twice the breadth and the height is 11 m. Find the area of the ceiling.

• 200 sq. m

• 300 sq. m

• 400 sq. m

• 500 sq. m

82. How many cubes each of surface 4 sq. cm can be made from a 8 cm cube?

• 16

• 3

• 64

• 12

83. is equal to

• 1

• 2

• 3

• 6

84. The distance between the tops of two trees 20 m and 28 m high is 17 m. The horizontal distance between the trees is

• 9 m

• 12 m

• 15 m

• 31 m

85. The average of 3 prime numbers between 50 and 75 is 191/1 Find the difference between the largest and the smallest prime numbers.

• No unique value

• 12

• 17

• 19

86. In a zoo 65% of the animals were mammals. Now after one year, only 60% mammals are alive. How many mammals are alive now if only 60% of the original 1200 animals are alive and no new animal is added to the zoo?

• 270

• 450

• 720

• 468

87. The compound interest on a certain sum for 2 years is Rs. 1100 and the simple interest is’ Rs. 1000. If this sum is invested such that simple interest is Rs. 400 and the number of years is equal to rate percent per annum, find the new rate per cent.

• 2%

• 4%

• 8%

• 16%

88. A sphere of radius 3 cm is dropped into a cylindrical vessel partly filled with water. The radius of the vessel is 6 cm. If the sphere is submerged completely, by how much will the surface of water be raised?

• 1 cm

• 2 cm

• 3 cm

• 6 cm

89. A grocer bought 10 kg of apples for Rs. 81 out of which one kg were found rotten. If he wishes to make a profit of 10%, then he should sell it at — per kg.

• Rs. 10

• Rs. 10.10

• Rs. 9.90

• Rs. 11

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