-
The height of a right circular cylinder is three times the radius of the base. If the height were four times the radius, the volume would be 1078 cubic centimetre more than it was previously. Find the radius of the base.
-
- 6 cm
- 5 cm
- 7.5 cm
- 7 cm
- 6 cm
Correct Option: D
Let the radius of base = r cm
∴ h1 = 3r cm.
h2 = 4r cm.
According to the question,
πr²h2 - πr²h1 = 1078
⇒ πr² (h2 - h1) = 1078
| ⇒ | r²(4r - 3r) = 1078 | |
| 7 |
| ⇒ | r³ = 1078 | |
| 7 |
| ⇒ r³ = | = 49 × 7 | |
| 22 |
∴ r = ³√49 × 7 = 7 cm.
