Question

the outer diameter of a drainage water pipe is 1.4 M and it is 35 M long find the cost of painting its outer surface @ rupees 1.50 per square metre

Answer 1

Outer diameter= 1.4m
Therefore radius= 1.4 ÷ 2 = 0.7m
Height (length)= 35m

CSA= 2πrh= 2× (22÷7) × 0.7 × 35
= 154m sq.

Cost= 1.50 × 154 = 231 /-

Answer 2

The cost of Painting Pipe is Rs. 231/-

Step-by-step explanation:

Given,

• The Diameter of the Cylindrical Pipe, d = 1.4 m

• The Radius (Half Diameter) of Cylinder becomes, r = $\frac {1.4}{2}$ = 0.7 m

• The Height/Length of Cylindrical Pipe, h = 35 m

We know that,  

Curved Surface Area is to be calculated, as the area is to be painted.

Curved Surface Area of Cylinder, CSA = $2 \pi \times Radius \times Height$

CSA = $2 \times \frac {22}{7} \times 0.7 \times 35$

CSA = $2 \times 22 \times 0.1 \times 35$

CSA = $2 \times 22 \times \frac {1}{10} \times 35$

CSA = $22 \times 7$

CSA = 154 $m^2$

• Cost of painting 1 $m^2$ = Rs. 1.5 /-

Hence, Cost of Painting the CSA of Cylinderical Pipe = $1.5 \times 154$

= Rs. 231/-