Problem:
Find the cost of polishing a circular piece of wood of diameter 1.4 m, if the rate of polishing is Rs 50 per square metre. (Take Pi=22/7)?

Solution:

To find the cost of polishing the circular piece of wood, we need to calculate its area and then multiply it by the rate of polishing per square meter. Let's break down the solution into steps:

Step 1: Calculate the radius:
The diameter of the circular piece of wood is given as 1.4 m. To find the radius, we divide the diameter by 2.
Radius = Diameter/2 = 1.4/2 = 0.7 m

Step 2: Calculate the area of the circular piece of wood:
The formula to calculate the area of a circle is:
Area = π * r^2
where π is a mathematical constant approximately equal to 22/7 and r is the radius.
Area = (22/7) * (0.7)^2 = (22/7) * 0.49 = 1.54 square meters (approx.)

Step 3: Calculate the cost of polishing:
The rate of polishing is given as Rs 50 per square meter.
Cost of polishing = Rate * Area = 50 * 1.54 = Rs 77 (approx.)

Therefore, the cost of polishing the circular piece of wood with a diameter of 1.4 m at a rate of Rs 50 per square meter would be approximately Rs 77.

Summary:
- The diameter of the circular piece of wood is 1.4 m.
- The radius is found by dividing the diameter by 2, which is 0.7 m.
- The area of the circular piece of wood is calculated using the formula π * r^2, where π is approximately equal to 22/7 and r is the radius. The area is approximately 1.54 square meters.
- The cost of polishing is calculated by multiplying the rate of polishing per square meter (Rs 50) with the area. The cost is approximately Rs 77.

D =1.4m
r = 1.4 ÷2 = 0.7
Circumference = 2× pi ×r
So,2 ×22/7 ×1.4/2