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Question

a wooden toy is in the form of cone surrounded on a hemisphere .the daimeter of the base of the cone is 6cm and its height is 4cm .find the cost of painting the toy at the rate of rs.50 @100cm square.

Answer 1

Basically, they tell you the diameter and the height of the cone and tell you to find the surface area.

I'm sure you have some kind of equation to calculate the surface area of a cone, but I don't and I don't want to give you half the answer, so I looked it up on google and I got that:

SA = pi*r*(l+r), where l is the slant height. (the length of the slant)

to find l, you have to use pythagoras theorem, c^2 = a^2 + b^2, where a and b are the radius and height. you have the diameter, so divide it by 2 to get the radius.

radius is 3cm, height is 4cm, so l^2 = 3^2 + 4^2 = 25, l=5 cm

so then surface area is pi*3cm*(5cm+3cm) = 24*pi (cm^2).

24*pi is about 75.4cm^2, so then you know that it costs rs. 50 per 100cm^2. First, find the price for 1cm^2, divide 50 rs by 100 to get rs 0.5, per cm^2. Now you have 75.4 cm^2, so multiply the rs 0.5 /cm^2 * 75.4cm^2.


total price = rs 37.7, round up I guess to get rs. 38. I am not sure if people still use paise there, but ya. Hope you understand.

Answer 2

4 pie R^2 x 1/2 for surface area of hemisphere
pie R x Side for the surface of the cone thats minus the bottom circle
the Side of the cone is 5 to find that its a triange if you look at it of height^2 + R^2 = Side^2 so 4^2 + 3^2 = Side^2 and 25= Side^2 and Side is 5

Answer 3

Slant height of cone = L
L² = 3² + 4² = 5²
L = 5 cm
Surface area of cone =πr(L + r) where r is the radius and L is the slant height.
Surface area of hemisphere = (1/2).4πr² = 2πr²
Total S.A.= πrL + 3πr² = πr.(L + 3r²)
Total S.A = 3π.(5 + 27) = 96π cm²
Cost of painting = (96π/100) x 50 = 48π = rs 150.80

Answer 4

$0.38
Please give me best answer thanks!