Question

The adjoining figure shows a wooden toy rocket which is in the shape of a circular cone mounted on a circular cylinder. The total height of the rocket is 26 cm, while the height of the conical part is 6 cm. The base of the conical portion has a diameter of 5cm, while the base diameter of cylindrical portion is 3cm. If the conical portion is to be painted green and the cylindrical portion red, find the area of the rocket painted with each of these colours. Also find
the volume of the wood in the rocket. Use π=3.14
and give answers correct to 2 decimal places.​

Answer 1

Vol. of wood

1/3πr^2h=.1/3πx 2.5^2 x6=12.50π

πr^2h=πx1.5^2 x 20 = 45π

Total vol = 12.5π+45π = 57.5

180.55cm3. vol. Ans

Area to be painted:

Conical Part: Green

I =v r2+h2 =v 2.5^2+6^2 = 6.25cm

πrl + π(R+r) (R-r)

πx 2.5x6.25 +π(2.5+1.5) (2.5-1.5)

15.625π + 4π

= 19.625π = 61-62cm2

conical Part Green=61.62cm2

cylindrical part Red:

2πrh+πr 2

2πx1.5x20 +πx1.5^2

60π +2.25π = 62.25π = 195.47cm2

cylindrical Part Red=195.47cm2