Question

9. If area of circle is 616sq.cm
find its circumference
O 67cm
O 88cm
O 68cm​

Answer 1

A N S W E R :

• The circumference of circle is 88 cm.

G I V E N :

• Area of circle = 616 cm²

T O F I N D :

• Circumference of circle = ?

S O L U T I O N :

• The area of circle has the formula = πr²
• The circumference of circle has the formula = 2πr

For finding the circumference of the circle first we should have radius.

Let radius of circle be 'r'

Let's find the radius from area given :

→ πr² = 616

→ 22/7 × r² = 616

→ r² = 616 × 7/22

→ r² = 4312 ÷ 22

→ r² = 196

→ r = √196

→ r = 14 cm

Now, we can use this value of r and plug in into the formula for circumference. Shown below:

→ Circumference of circle = 2πr

→ Circumference of circle = 2 × 22/7 × 14

→ Circumference of circle = 2 × 22 × 2

→ Circumference of circle = 88 cm

⛬ The circumference of circle is 88 cm.

Answer 2

Given :

• Area of circle is 616 cm²

To Find :

• Circumference of circle

Solution :

• Let the radius be ' r '

$\bigstar \: \large{\sf{\underline{\red{Area\:of\:Circle\:=\:π{r}^{2}}}}}$

$\leadsto \sf 616\:=\: \dfrac{22}{7} \times {r}^{2}$

$\leadsto \sf {r}^{2}\:=\: \dfrac{616 \times 7}{22}$

$\leadsto \sf {r}^{2}\:=\: \cancel \dfrac{4312}{22}$

$\leadsto \sf {r}^{2}\:=\:196$

$\leadsto \sf r\:=\: \sqrt{196}$

$\bigstar \: \large{\sf{\underline{Radius\:=\:14\:cm}}}$

$\bigstar \: \large{\sf{\underline{\red{Circumference\:of\:Circle\:=\:2πr}}}}$

$\leadsto \sf Circumference\:of\:circle\:=\:2 \times \dfrac{22}{7} \times 14$

$\leadsto \sf Circumference\:of\:circle\:=\: 2 \times 22 \times 2$

$\bigstar \: \large{\sf{\underline{\red{Circumference\:of\:circle\:=\:88\:cm}}}}$

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