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प्रश्न
The height of a cone is 21 cm. Find the area of the base if the slant height is 28 cm.
उत्तर
Given that
Slant height ‘l’ = 28 m.
Height of cone (h) = 21cm
∴ Radius of cone (r)=`sqrt(28^2-21^2)` [by Pythagoras theorem]
= `7sqrt(7cm)`
∴ Area of base = `pir^2`
= `22/7xx(7sqrt7)^2`
= `22/7xx7xx7=1078 cm^2`
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