A cylindrical tank has an internal radius of 3.5 m and a height of 8 m. If the tank is 75% filled with water, what is the volume of the water in it? (Take \(\pi=\frac{22}{7}\))
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 231 m3
The volume of a cylinder is \(\pi r^2h\); the water fills 75% of it.
Volume of the tank \(\displaystyle=\frac{22}{7}\times3.5\times3.5\times8=38.5\times8=308\) m3
Water \(=75\%\) of \(308=\displaystyle\frac{3}{4}\times308=231\) m3
Why the other options are incorrect
Option (1) 308 m3 — Incorrect. This is the volume of the whole tank, not 75% of it.
Option (3) 77 m3 — Incorrect. This is the empty 25% of the tank.
Option (4) 924 m3 — Incorrect. This uses the diameter 7 m as the radius: \(\frac{22}{7}\times49\times8\times\frac{3}{4}=924\).