MAH MCA CET 2024
The curved surface area of a glass having radii 3cm and 4cm respectively and slant height 10cm is
Answer (Detailed Solution Below)View answer ▾Hide ▴
Answer: Option C — 220 cm²
Detailed Solution
The glass is a frustum of a cone, so .
.
With : cm .
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, which matches only option (C).⚠ Common trap
Option (B), 110 cm², comes from halving: , as if the formula were the area of a triangle.Quick tip
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Ask a doubtMore Volume & Surface Area Questions
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Volume & Surface Area — Preparation
This question tests your understanding of Volume & Surface Area, a key topic in the Quantitative Aptitude section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers the mensuration of three-dimensional solids: cubes, cuboids, cylinders, cones, spheres, hemispheres and frustums. You need to know the formulas for the volume, curved surface area and total surface area of each solid. For example, the volume of a cylinder is pi r^2 h and the volume of a sphere is (4/3) pi r^3. Exam questions test direct use of the formulas, melting one solid and recasting it into others (the volume stays the same), the number of small solids that can be made from a larger one, the effect of changing dimensions, water flowing through a pipe into a tank, and the cost of painting or covering a surface. When every length of a solid is multiplied by k, its surface area is multiplied by k^2 and its volume by k^3. This fact solves many questions about changing dimensions in a single step. Practise the volume and surface area questions below, each with a step-by-step solution.