You will need
  • Calculator, ruler, tape measure, meter.
If a math problem you know the area of a circleand need to find the diameter, use the following formula: s=pi*r^2, where s is the area of a circle (units: square meters, square centimeters, square millimeters), r is the radius of the circle (the segment that connects the center of the circle with its boundary, measured in meters, centimeters, millimeters), pi - mathematical constant, the decimal system is approximately equal to 3.14.
From this formula we Express r (should get the following formula: r=square root of (s/pi)). Substitute into it the known values, find r and compute the diameter of a circleby multiplying the radius by two (d=2*r).
By analogy solve the following problem. Task: Find the diameter of a circleif you know its area (s=12.56 cm). Check whether you have solved it. Answer: d=8 centimeters.
For example, you face the problem, which is known to the circumference, and need to find its diameter, then use the following formula: c=2*pi*r, where C is the circumference (units of measurement: meters, centimeters, millimeters). From this formula we Express r (come up with the following formula: r=c/(2*pi). Substitute it that has already been given, find r and compute the diameter of a circleby multiplying the radius by two (d=2*r).
Solve the following problem. Problem: Find the diameter of a circle if you know its length (C=12.56 cm). Check the correctness of its decision. Answer: d=4 cm.
If you need to measure the diameter of the circle, not theoretically, but practically, use a ruler, tape measure or meter. The range is the simplest measurement tool which is a plate with printed graduations. Roulette is collapsible into a circle of tape with marks for measurements, the meter is the ruler in centimeters for measuring.