In the given problem a toy is in the form of a cylinder with hemispherical ends for that to find total cost we need to use cylinder and hemispherical surface area formula. Question number 18 from RS Aggarwal book page number 789, chapter volume and surface area of solid.
Deepak BoraNewbie
A toy is in the form of a cylinder with hemispherical ends. If the whole length of the toy is 90 cm and its diameter is 42 cm, then find the cost of painting the toy at the rate of 70 paise per sq cm.
Share
Total height of toy = 90cm.
Height of cylinder = 90 – (2 * 21)
= 48cm
Area of cylinder =2πrh
= 2 * 22/7 * 21 * 48
= 6336 cm²
Area of hemisphere =4 π r²
= 4 * 22/7 * 21²
= 5544 cm²
Total area = 6336 +5544
= 11880
= 11880 cm²
Cost = 11880 * 70
= 831600 paise
= 8316 rupees
∴ Cost of painting the toy is 8316 rupees