Class 9 Maths Questions and Answers with Explanation Paper

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Topic: Surface areas and volumes

Class: 9th

Q. 1 What is the lateral surface area of a cuboid with dimensions l, b and h.

Solution.

As we know that a cuboid has six rectangular faces, so its lateral surface area will be the sum of these 6 rectangles.

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Lateral surface area of cuboid = Area of rectangle1 + Area of rectangle 2 + Area of rectangle 3+ Area of rectangle 4+ Area of rectangle 5+ Area of rectangle 6

Q. 2 The Length, breadth and height of a room are 5m, 4m and 3m respectively. Find the cost of whitewashing the walls of the room and the ceiling at the rate of Rs. 7.50 per metre square.

Sol. Given.

Length of room

Breadth of room

Height of room

• Area of four walls metre square

• Area of ceiling metre square

• Total area to be white washed = Area of four walls Area of ceiling

• metre square

• Cost of whitewashing the room

• Cost for 1metre square =Rs. 7.50

• Cost for74 metre square

• So, cost of whitewashing the walls of room and ceiling is Rs. 555