yangsta8 wrote:
Car B begins moving at 2 mph around a circular track with a radius of 10 miles. Ten hours later, Car A leaves from the same point in the opposite direction, traveling at 3 mph. For how many hours will Car B have been traveling when car A has passed and moved 12 miles beyond Car B?
A. 4pi – 1.6
B. 4pi + 8.4
C. 4pi + 10.4
D. 2pi – 1.6
E. 2pi – 0.8
The OA is pretty long and even solving it that way takes me +2 mins. Hopefully someone can offer a fast solution.
d = 2*pi*r = 20pi
let pi = 3 (roughly), hence d would be 66
after 10 hrs B would have travelled 20 miles, so remaining d = 46
A travels in opposite direction, so inorder to meet time taken would be 46/2+3 = 9.2
time for further 12 miles would be 12/2+3 = 2.4
B has already been travelling for 10 hours, so total time = 9.2+2.4+10 = 21 (approx)
from answer choices B and C are closest
B is 4pi +8.4 => 12+8.4 = 20.4
C is 4pi + 10 => 12+10.4 = 22.4
Since B is closer, I went with B