Ex.11.3 Q6 Perimeter and Area - NCERT Maths Class 7

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Question

Saima wants to put a lace on the edge of a circular table cover of diameter \(1.5 \rm\,m.\) Find the length of the lace required and also, find its cost if one meter of the lace costs \(\rm Rs. \,15.\) (Take \(π = 3.14\))

 Video Solution
Perimeter And Area
Ex 11.3 | Question 6

Text Solution

What is known?

Diameter of the circular table and cost of one meter of lace.

What is unknown?

The length of the lace required and the overall cost of lace if the cost of one meter of the lace is \(₹\,15.\)

Reasoning:

Since Saima wants to put lace on the edge of the circular table cover, that means length of the lace will be equal to the circumference of circular table cover. Find circumference of circle using the radius of the circular table cover. Now, to find the overall cost of lace multiply the total length of lace by\( ₹\,15.\)

Steps:

Given, Diameter of the circular table cover

\(= 1.5 \rm\,m\)

Radius of the circular table cover

\(\begin{align}=\frac{1}{2}\end{align} \rm \,m = 0.75\rm\, m\)

Circumference of circular table cover

\[\begin{align}&= 2\pi r\\&= 2 \times 3.14 \times 0.75\\ &= 4.71\end{align}\]

Therefore, the length of required lace is \(4.71 \rm\,m.\)

Since the cost of \(1\rm\, m\) lace is \(₹ \,15\)

Therefore, the cost of \(4.71 \rm\,m \) lace

 \(= ₹\,15\, \times\, 4.71 = ₹ \,70.65\)