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Question
A wooden toy is in the form of a cone surmounted on a hemisphere. The diameter of the base
of the cone is 16 cm and its height is 15 cm. Find the cost of painting the toy at Rs. 7 per 100
`cm^2`.
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Solution 1
Diameter of cone = 16cm.
∴ Radius of cone = 8cm.
Height of cone = 15cm
Slant height of cone - `sqrt(8^2+15^2)`
-`sqrt(64+225)`
-`sqrt(289)`
-17 cm
∴ Total curved surface area of toy
-πrl + `2πr^2`
-`22/7 × 8 × 17 + 2 × 22/7 × 8^2`
- `5808/7cm^2`
Now .cost of `100cm^2 - Rs.7`
`1cm^2 - Rs7/100`
Hence , cost of `5808/7 cm^2 - Rs (5808/7×7/100)`
-Rs.58.08.
Solution 2
Diameter of cone = 16cm.
∴ Radius of cone = 8cm.
Height of cone = 15cm
Slant height of cone - `sqrt(8^2+15^2)`
-`sqrt(64+225)`
-`sqrt(289)`
-17 cm
∴ Total curved surface area of toy
-πrl + `2πr^2`
-`22/7 × 8 × 17 + 2 × 22/7 × 8^2`
- `5808/7cm^2`
Now .cost of `100cm^2 - Rs.7`
`1cm^2 - Rs7/100`
Hence , cost of `5808/7 cm^2 - Rs (5808/7×7/100)`
-Rs.58.08.
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