Question

15. The external and internal diameters of a hollow
cylindrical pipe are 10 cm and 8 cm respectively
its length will be 21 cm, then find the metal used in formation​

Answer 1

Step-by-step explanation:

Given:

$i) external \: diameter = 10 cm</p><p> \\ then \: it's \: radius (r) = 5 cm \\ </p><p>ii) internal diameter = 8 cm</p><p> \: \\ then \: it's \: radius (R) = 4 cm \\ </p><p>iii) height (h)= 21cm \\ \\ </p><p></p><p>metal \: used = π {r}^{2}h \: - \\ \: \pi {R}^{2} h \\ \: \: \: = \frac{22}{7} \times 5 \times 5 \times 21 \: - \: \frac{22}{7} \times 4 \times 4 \times 21 \\ = \frac{22}{7} \times 21 \times (5 \times 5 - 4 \times 4) \\ = 22 \times 3 \times (25 - 16) \\ = 66 \times (9) \\ = 594 \: c {m}^{3}$