Ex.11.3 Q17 Perimeter and Area - NCERT Maths Class 7

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Question

The minute hand of a circular clock is \(15 \rm\,cm\) long. How far does the tip of the minute hand move in \(1\) hour? (Take \(π = 3.14\))

Text Solution

What is known?

The minute hand of a circular clock is \(15 \rm\,cm\) long.

What is unknown?

Distance covered by tip of minute hand in \(1\) hour.

Reasoning:

In one hour, the minute hand completes one full circle. So, the distance covered by tip is equal to the circumference of the circle.

Steps:

Radius of the circle \((r) =\) \(15 \rm\,cm\)

Circumference of circular clock

\[\begin{align} &= 2\pi r \\ &= 2 \times 3.14 \times 15\\ &= {\rm{ }}94.2{\rm{ }}\rm\,cm\end{align}\]

Therefore, the tip of the minute hand moves \(94.2 \rm\,cm\) in \(1\) hour.