Question

the radius of a circular region is 7 cm find its area in metres

Answer 1

$\frac{22}{7} X7X7 \\ =22X7 \\ =154$Heya.

Your answer is here.

There are two methods for solving this.
In first, first we will convert radius (in cm) into radius (in m). Then we will calculate area from it.
In second, first we will calculate area from given radius, after area is obtained. we will covert area (in cm²) to area in m².

METHOD I :-

Given Radius - 7 cm.
7 cm = 7/100 m.  (bcoz 1 cm= 1/100 m).

Area of Circle = πr²
$= \frac{22}{7} X \frac{7}{100} X \frac{7}{100} \\ =\frac{11}{50} X \frac{7}{100}$
= 77/5000
= 0.0154 m².
Hence, the area of circle is 0.0154 m².
 
METHOD II :-

Given radius = 7 cm
Now, using formula mentioned above.
Area = 22/7 X 7 X7
= 22 X 7
= 154 cm².

Now, we will convert this area (given in cm²) into area (in m²).
As we know that 1 m²= 10000 cm².
So, 154 cm² ,
 154 X 1/10000
= 154/10000
= 0.0154 m².

Hence, the area is same by both steps. 
Whichever, you find easy use that.

Hope I helped...
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