Answer: OPTION 1
Step-by-step explanation:
For this exercise you need to remember that, by definition, the Arc length can be calculated with the following formula:

where "C" is the central angle of the arc in radians and "r" is the radius.
Since you need to find the Central angle, you have to solve for "C" from that formula, as following:

According to the information given in the exercise, you can identify that:

Therefore, the final step is to substitute these values into the formula and evaluate, in order to find the value of "C":

Answer:
8cm
Step-by-step explanation:
The radius is always half the length of the diameter
4*2=8
Answer:
20 * 10⁻⁹
Explanation:
Assume that the number of times is t
Now, we want to know what number (t) multiplied by 2 * 10¹⁴ will result in
4 * 10⁶
Translating this into an equation:
2 * 10¹⁴ * t = 4 * 10⁶
Solving for t:
t = (4 * 10⁶) / (2 * 10¹⁴)
t = 20 * 10⁻⁹
Hope this helps :)
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