1. By the condition of the problem, it is known that the radius of the circle is 6.5 cm.
2. Let’s apply the trigonometric formula:
the length of a circle L is equal to twice the product of the number P and the radius of the circle R.
Substitute the given value R into the general formula and get
L = 2 * 3.1 * 6.5cm = 40.3cm.
Let’s calculate the length of the arc according to the rule: to find a part of a number, you need to multiply this number by a fraction equal to this part:
0.4 L = 40.3 cm * 0.4 = 40.3 cm * 4: 10 = 16.2 cm.
Answer: 0.4 part of a given circumference is 16.2 cm.
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