Answer:
12.5
Step-by-step explanation:
Let individual time taken by Anthony, Brian and Chris = t1 , t2 , t3 respectively
So, total time taken by A & B = 1 / t1 + 1 / t2 , lets suppose = 10 {i}
Total time taken by A & C = 1 / t1 + 1 / t3 , lets suppose = 15 {ii}
Total time taken by B & C = 1 / t2 + 1 / t3 , lets suppose = 20 {iii}
From {i} , 1 / t2 = 10 - 1 / t1
From {ii} 1 / t1 = 15 - 1 / t3
By above two eqtns , 1 / t2 = 10 - (15 - 1 / t3)
1 / t2 = 1 / t3 - 5
Putting in {iii} , 1 / t3 - 5 + 1 / t3 = 20
2 / t3 = 25
t3 = 12.5
