Question

^{The curved surface of a cylindrical bulb of height 18cm and base radius 7 cm is to be painted in luminating gold colour such that 2/3 rd of the height of bulb emits golden light, painting is done at Rs. 5 per sq. cm. The cost of painting the bulb is (pi =$\frac{22}{7}$)}

• A. Rs.2640
• B. Rs.1650
• C. Rs.2750
• D. Rs.2800

Answer 1

The correct option is A

Rs.2640

Curved Surface area of the bulb=2πrh = 2× $\frac{22}{7}$ ×7 × 18 = 792 $c{m}^2$

Area to be painted= (2/3) × 792 = 528 sq. cm

Total cost = 528 × 5= Rs.2640