Class 9 Maths Questions and Answers with Explanation Paper (For CBSE, ICSE, IAS, NET, NRA 2022)
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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.
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 ₹ 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 = ₹ 7.50
- Cost for74 metre square
- So, cost of whitewashing the walls of room and ceiling is ₹ 555