Step-by-step explanation:
there is no diagram here.
I assume that the race track is a rectangle in the middle and two half-circles at the left and right ends, and that the length of the rectangle is D = 2R. which makes the rectangle actually a square, as the width is the diameter of the (half-)circles, which is also 2R.
Sonic ran the track 5 times in 10 seconds with a speed of 321 m/s.
that means he ran 10×321 m in 10 seconds = 3210 m.
so, 5 times the track is 3210 m, which means that the track itself is 3210/5 = 642 m long.
and based on the assumptions above the track consists of 2 times the length of the rectangle (or square), and the full circumference of a circle with radius R (2 half-circles make one full circle).
we know the formula for the circumference of a circle :
2×pi×radius
so, we have then
642 = 2×2R + 2×pi×R = R×(4 + 2×pi)
R = 642 / (4 + 2×pi) = 62.43201701...
and when using the requested "cut-off" pi = 3.14, we get
R = 642 / (4 + 2×3.14) = 62.45136187...
and that is rounded 62.5
so, the second answer option is correct.
