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प्रश्न
Two identical cubes each of volume 64 cm3 are joined together end to end. What is the surface area of the resulting cuboid?
उत्तर
Let the side of one cube = a
Surfaces area of resulting cuboid = 2(Total surface area of a cube) – 2(area of single surface)
We know that,
Total surface area of cube = 6a2, where a = side of cube
⇒ Surfaces area of resulting cuboid = 2(6a2) – 2(a2) = 10a2
Also,
According to the question,
Volume of cube = 64 cm3
Volume of cube = a3
64 = a3
a = 4 cm
Therefore, surface area of resulting cuboid = 10a2 = 10(4)2 = 160 cm2
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No Question.
Choose the correct answer of the following question:
The surface areas of two spheres are in the ratio 16 : 9. The ratio of their volumes is
Assertion (A)
The curved surface area of a cone of base radius 3 cm and height 4 cm is 15π cm2.\
Reason (R)
Volume of a cone = πr2h
- Both Assertion (A) and Reason (R) are true and Reason (R) is a correct explanation of Assertion (A).
- Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).
- Assertion (A) is true and Reason (R) is false.
- Assertion (A) is false and Reason (R) is true.
A cylindrical pencil sharpened at one edge is the combination of ______.
The radius of a metallic sphere is 8 cm. It was melted to make a wire of diameter 6 mm. Find the length of the wire.
Find the surface area of a sphere of radius 7 cm.
Solution :
The surface area of the sphere = 4πr2
= `4 xx 22/7 xx square^2`
= `4 xx 22/7 xx square`
= `square xx 7`
∴ The surface area of the sphere = `square` sq.cm.
