Question

8. Two solids of right cylindrical shape are 49 cm and 35 cm high and their base
diameters are 16 cm, 14 cm respectively. Both are melted and moulded into a
single cylinder, 56 cm high. Find its base diameter.
9. The volume of a metallic cylindrical pipe is 748 cm3. Its length is 14 cm and its
external radius is 9 cm. Find its thickness.
10. The volume of a cylinder is 150t cu. cm and its height is 6 cm. Find the areas of its
total surface and lateral (curved) surface.
2
11. The curved surface area of a cylindrical pillar is 264 m2 and its volume is 924 m3.
Find the diameter and the height of the pillar.
​

Answer 1

Step-by-step explanation:

Let r1 and r2 be the respective radii of first and second cylinder.

Diameter of 1st cylinder = 16 cm 

Radius = r1 = 16/2 = 8 cm

Diameter of 2nd cylinder = 14 cm

Radius = r2 = 14/2 = 7 cm

Height of 1st cylinder = h1 = 49 cm

Height of 2nd cylinder = h2 = 35 cm

Volume of 1st cylinder = πr1²h

⇒ (22*8*8*49)/7

⇒ 9856 cm³

Volume of 2nd cylinder = πr2²h

⇒ (22*7*7*35)/7

⇒ 5390 cm³

Total volume = 9856 cm³ + 5390 cm³ = 15246 cm³

Let radius of new cylinder be r.

⇒ Volume of 1st and 2nd cylinder = Volume of the new cylinder

⇒ 15246 cm³ = (22*r²*56)/7

⇒ r² = 106722/1232

⇒ r² = 86.625 cm

⇒ r = √86.625

⇒ r = 9.307 cm

⇒ diameter = 9.307*2 = 18.614 cm

So, the diameter of the new cylinder is 18.614 cm

That's your answer..

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