Question points
Points A and B lie on a circle with radius 1, and arc 
has length 
. What fraction of the circumference of the circle is the length of arc ?
Points A and B lie on a circle with radius 1, and arc has length .
Hard-difficulty · SAT Math · Circles — Arc length and sector area. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.
Answer explanation
The correct answer is 
. The circumference, C, of a circle is 
, where r is the length of the radius of the circle. For the given circle with a radius of 1, the circumference is 
, or 
. To find what fraction of the circumference the length of arc is, divide the length of the arc by the circumference, which gives 
. This division can be represented by 
. Note that 1/6, .1666, .1667, 0.166, and 0.167 are examples of ways to enter a correct answer.
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