A bicyclist travels 8 miles due west at a constant speed. Next, she rides x miles in a straight line in a direction somewhere between north and east, traveling at half the speed. She stops when she is due north of her starting point, at which time she is y miles from her original location. She then rides, at 1/3 of her original speed, due south for x/2 miles, at which point she ends her trip, more than x/3 miles from her starting point.
If x and y are integers, how many total miles did she cycle?
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8^2 + y^2 = x^2
8^2 = (x^2 - y^2) = (x+y)(x-y)
Case 1: y > x/2 + x/3 = 5x/6
Case 2: x/2 > y + x/3 ; y < x/2 - x/3 = x/6
1: x + y = 16; x - y = 4; x = 10; y = 6; x/6 = 10/6 = 5/3; 5x/6 = 25/3 = 8 1/3; Not feasible since no cases are possible
2. x+ y = 32; x- y=2; x = 17; y = 15; x/6 = 17/6 = 2 5/6; 5x/6= 85/6 = 14 1/6; y=15 > 5x/6=14 1/6; Feasible
Total distance travelled = 8 + x +x/2 = 8 + 17 + 17/2 = 25 + 8.5 = 33.5 miles
IMO D