Question

The number of iron rods, each of length \[7m\] and diameter \[2m\] that can be made out of \[0.88\] cubic meters of iron is \[\left( \pi =\dfrac{22}{7} \right)\]
a)300
b)400
c)500
d)600

Answer 1

Hint: As the iron rod is in the shape of a cylinder so use formulas of cylinder. Its curved surface area formula. And if we divide total volume of iron rod with volume of rode we will get total number of iron rods.

Complete step-by-step answer:
Length of the iron rode \[=7\,m\]
Diameter of iron rod \[=2\,m\]
As \[\dfrac{diameter}{2}\]
So, Radius \[=\dfrac{2}{2}=1m\]
Volume of the rod \[=\]\[\pi \]\[{{r}^{2}}\]\[h\]
So, by putting the values of and r in the formula,
Volume \[=\dfrac{22}{7}\times {{\left( \dfrac{1}{100} \right)}^{2}}\times 7=\dfrac{11}{5000\,}cu.\,m.\]

Volume of iron \[=0.88\,cu.m.\]
So, number of rods \[\dfrac{volume\,of\,iron}{volume\,of\,one\,iron\,rod}\]
Number of rods \[=0.88\times \dfrac{5000}{11}=400\,rods\]

Note: Always see that the given solid shape is in which shape then put the correct formula and solve it. These are two cases in maximum shapes like curved surface area and total surface area, so be confirm which is asking in the question.