Diameter of cylinder A is 7 cm and the height is 14 cm. Diameter of cylinder B is 14 cm and height is 7 cm. Without doing any calculations can you suggest whose volume is greater? Verify it by finding the volume of both the cylinders. Check whether the cylinder with greater volume also has greater surface area.

Yes, we can say that volume of cylinder B is greater, since radius of cylinder B is
greater than that of cylinder A (and square of radius gives more value than
previous).
Diameter of cylinder A = 7 cm
⇒ Radius of cylinder A = 7/2cm
And Height of cylinder A = 14 cm
∴ Volume of cylinder A = πr²h = 22/7×7/2×7/2×14
= 539 cm³
Now Diameter of cylinder B = 14 cm
⇒ Radius of cylinder B = 14/2 = 7cm
And Height of cylinder B = 7 cm
∴ Volume of cylinder A = πr²h = 22/7x7x7x7
= 1078 cm³
Total surface area of cylinder A = πr(2h+r)
[∵ It is open from top]
22/7×7/2(2×14+7/2)=11x(28+7/2)
= 11×63/2=346.5 cm²
Total surface area of cylinder B = 𝜋r(2h+r) [∵It is open from top]
= 22/7×7(2×7+7)
22x (14+7) = 22×21 = 462cm²
Yes, cylinder with greater volume also has greater surface area.

Class 8 Maths Chapter 11 Exercise 11.4 Solution in Video

for more answers vist to:
https://www.tiwariacademy.com/ncert-solutions/class-8/maths/chapter-11/