A metal sphere of diameter 15 cm is melted down and recast into hollow cylindrical pipe of external radius 7.5 cm and internal radius 3 cm. In the process 12% of the metal is lost. Calculate the volume of metal used to make the pipe.

Rediasi ya tufe $R_{tufe}$ ni nusu ya kipenyo.

Fomula ya ujazo wa tufe ni $V = \frac{4}{3} \pi R^3$.

Asilimia ya chuma iliyotumika ni $100\% - 12\% = 88\%$.

Ujazo wa chuma kilichotumika kutengeneza bomba ni $\boxed{495 \pi \text{ cm}^3}$.

Rediasi ya nje $R = 3 \text{ cm}$.
Rediasi ya ndani $r = 2.3 \text{ cm}$.

Eneo la msalaba la chuma ni tofauti kati ya eneo la duara la nje na eneo la duara la ndani.

Eneo la msalaba la chuma kwenye bomba ni $\boxed{3.71 \pi \text{ cm}^2}$.

Ujazo wa bomba ni sawa na ujazo wa chuma kilichotumika.

Ambapo $h$ ni urefu wa bomba.

Gawanya pande zote mbili kwa $3.71 \pi \text{ cm}^2$:

Kumbuka kuwa $1 \text{ m} = 100 \text{ cm}$.

Kuzungusha kwa sehemu mbili za desimali:

Urefu wa bomba ni $\boxed{1.33 \text{ m}}$.