Question

the radius and slant height of a cone are in the ratio 4:7 if it's curved surface area is 792cm2find it's radius

Answer 1

the formulae for curved surface area. is22/7×r×l
let the ratio be x
r=4x. and l=7x
A to Q
22/7 ×4x×7x=792
22/7×28x=792
22×4x=792
x=792/22×4
x=144cm

Answer 2

Step-by-step explanation:

Given

The radius and slant of height of a cone are in the ratio 4:7

Curved Surface Area is 792 cm²

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To Find

The radius

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Solution

Let's consider the radius to be '4x' and height be '7x' (Here we have taken the radius as 4x and 7x since they are in the ratio of 4:7)

Formula to find the curved surface area of a cone ⇒ πrl

Here,

'r' stands for radius.

'l' stands for the slant height.

Curved surface area of the cone ⇒ 729 cm²

Let's solve the equation step-by-step

22/7×4x×7x =792

Step 1: Simplify the equation.

⇒ 22/7 4x × 7x = 729

⇒22/7×28x² =729

=22×4x²= 792

=88x²=792

Step 2: Divide 88 from both sides of the equation.

⇒ 88x²/88 = 792/88

Step 3: Find the square root of 9.

⇒ x=√9

= x=3

∴ The radius ⇒ 4x ⇒ 4(3) ⇒ 12 cm

∴ The slant height of cone ⇒ 7x ⇒ 7(3) ⇒ 21 cm

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