The sum of the radius and slant height of a cone is square of the height of the cone while the difference between the radius and slant height is 1 cm only. What is the total surface area (in cm²) of the cone having height of 9 cm? (Take π = 22/7) Rounded off to 2 decimal places.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e 10,182.86.
r + l = 81 ..........(1)
l - r = 1 ..........(2)
Add both equation
(r + l) + (l - r) = 81 + 1
⇒ 2l = 82 → l = 41
Then, r = 81 - l = 81 - 41 = 40
Total Surface Area = πr(l + r) = (22/7) × 40 × (41 + 40) = (22/7) × 40 × 81 = (22 × 40 × 81) / 7
⇒ 71280 / 7 = 10182.86 cm²