| A rope makes 70 rounds of the circumference of a cylinder whose radius of the base is 14 cm. How many times can it go round a cylinder with radius 20 cm? |
A) 40
B) 49
C) 100
D) None of the above
Correct Answer: B
Solution :
| Let the required number of rounds be x. |
| More radius, Less rounds [Indirect proportion] |
| \[\therefore \] \[\begin{matrix} 20:14 & :: & 70:x \\ \end{matrix}\] |
| \[\Rightarrow \] \[20\times x=14\times 70\] |
| \[\Rightarrow \] \[x=\frac{14\times 70}{20}\]\[\Rightarrow \]\[x=49\] |
| Hence, the required number of rounds is 49. |
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