Question

kindly give correct answer​

Answer 1

Given :-

• The curved surface area of a cylinder is 7920 cm² and the circumference of the base is 126 cm.

To Find :-

• What is the height of the cylinder.

Formula Used :-

• $\boxed{\bold{\large{Circumference\: of\: a\: circle\: =\: 2{\pi}r}}}$
• $\boxed{\bold{\large{C.S.A\: of\: a\: cylinder\: =\: 2{\pi}rh}}}$

Solution :-

• C.S.A of a cylinder = 7920 cm²
• Circumference of a base = 126 cm
• First, we have to find the radius,

According to the question by using the formula we get,

⇒ $\sf126\: =\: 2 \times \dfrac{22}{7} \times r$

⇒ $\sf126\: =\: \dfrac{44}{7} \times r$

⇒ $\sf{\cancel{126}}\: \times \dfrac{7}{\cancel{44}} =\: r$

⇒ $\sf2.87 \times 7 =\: r$

⇒ $\sf20.09 (approx) =\: r$

➠ $\small\bf{\underbrace{\red{r\: =\: 20.09}}}$

• Hence, the radius of a cylinder is 20.09 cm .
• Now, we have to find the height of a cylinder,

Given :-

• Radius of a cylinder = 20.09 cm
• C.S.A of a cylinder = 7920 cm²

According to the question by using the formula we get,

↦ $\sf7920\: =\: 2 \times \dfrac{22}{7} \times 20.09 \times h$

↦ $\sf7920\: =\: \dfrac{44}{7} \times 20.09 \times h$

↦ $\sf{\cancel{7920}}\: \times \dfrac{7}{\cancel{44}} = 20.09 \times h$

↦ $\sf1260\: =\: 20.09 \times h$

↦ $\sf\dfrac{\cancel{1260}}{\cancel{20.09}} =\: h$

↦ $\sf62.8 (approx) =\: h$

➦ $\small\bf{\underbrace{\red{h\: =\: 62.8}}}$

$\therefore$ The height of a cylinder is 62.8 cm .

Answer 2

Answer:

circumference=126cm

2pie r=126cm

c.s.a.=7920cm^2

2pie rh=7920cm^2

126h=7920cm^2

so, h=7920/126=62.85cm. ans..

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