Question 52
Two tigers, Alice and Betty, run in the same direction around a circular track of circumference $400$ meters. Alice runs at a speed of $10~\mathrm{m}/\mathrm{s}$ and Betty runs at $15~\mathrm{m}/\mathrm{s}$. Betty gives Alice a $40$ meter headstart before they both start running. After $15$ minutes, how many times will they have passed each other?
(a) 9
(b) 10
(c) 11
(d) 12
(a) 9
(b) 10
(c) 11
(d) 12