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Mathematics

Assertion (A) : The total surface area of a right circular cone of slant height 13 cm and radius 5 cm is 90 π cm2.

Reason (R) : Curved surface area of a right circular cone is given by πr(l + r).

  1. A is true, R is false

  2. A is false, R is true

  3. Both A and R are true

  4. Both A and R are false

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Answer

Given,

Radius, r = 5 cm

Slant height, l = 13 cm

Total surface area = πrl + πr2

= πr(l + r)

= πr(l + r)

= π5(13 + 5)

= π5(18)

= 90π cm2.

∴ Assertion (A) is true.

By formula,

Curved surface area of a right circular cone = πrl

∴ Reason (R) is false.

Hence, option 1 is the correct option.

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