Question 70
Radius of cross section of a solid right circular cylindrical rod is 3.2 dm. The rod is melted and 44 equal solid cubes of side 8 cm are formed. The length of the rod is (Take Π = 22/7)
Solution
Let length of cylindrical rod = $$h$$ cm and radius = $$r$$ = 3.2 dm = 32 cm
Edge of cube = $$a=8$$ cm
Volume of cylindrical rod = $$44 \times $$ Volume of cube
=> $$\pi r^2 h= 44 \times a^3$$
=> $$\frac{22}{7} \times (32)^2 h = 44 \times (8)^3$$
=> $$(32)^2 h=44 \times (8)^3 \times \frac{7}{22}$$
=> $$h=\frac{14 \times (8)^3}{(32)^2}$$
=> $$h=\frac{14}{2}=7$$ cm
=> Ans - (B)
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