# A hollow iron pipe is 21 cm long and its external diameter is 8 cm. If the thickness of the pipe is 1 cm and iron weights 8 g/cm^{3}, then the weight of the pipe is:

A. 3.6 kg

B. 3.696 kg

C. 36 kg

D. 36.9 kg

**Answer: Option B **

__Solution(By Examveda Team)__

$$\eqalign{
& {\text{External}}\,{\text{radius}} = 4\,cm \cr
& {\text{Internal}}\,{\text{radius}} = 3\,cm \cr
& {\text{Volume}}\,{\text{of}}\,{\text{iron}} \cr
& = \left( {\frac{{22}}{7} \times \left[ {{{\left( 4 \right)}^2} - {{\left( 3 \right)}^2}} \right] \times 21} \right)c{m^3} \cr
& = \left( {\frac{{22}}{7} \times 7 \times 1 \times 21} \right)c{m^3} \cr
& = 462\,c{m^3} \cr
& \therefore {\text{Weight}}\,{\text{of}}\,{\text{iron}} = \left( {462 \times 8} \right)gm \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 3696\,gm \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 3.696\,kg \cr} $$
### Click here to read 1000+ Related Questions on Volume and Surface Area(Arithmetic Ability)

Related Questions on Volume and Surface Area

A. 12$$\pi$$ cm^{3}

B. 15$$\pi$$ cm^{3}

C. 16$$\pi$$ cm^{3}

D. 20$$\pi$$ cm^{3}

**In a shower, 5 cm of rain falls. The volume of water that falls on 1.5 hectares of ground is:**

A. 75 cu. m

B. 750 cu. m

C. 7500 cu. m

D. 75000 cu. m

A. 720 m^{3}

B. 900 m^{3}

C. 1200 m^{3}

D. 1800 m^{3}

A. 84 meters

B. 90 meters

C. 168 meters

D. 336 meters

## Join The Discussion