If both A and B are expanded to five times, the score is:
5a×5b/(5a+5b)
=25ab/[5(a+b)]
=5ab/(a+b)
The value of the score is five times that of the original.
Solution 2: 20 minutes = 1/3 hours, the original speed is a/b km/ hour, the time to arrive 20 minutes earlier is (b- 1/3) hours, and the speed to arrive 20 minutes earlier is a/(b- 1/3)km/ hour.
A/(b-1/3)-a/b = 3a/(3b-1)-a/b (km/h)
Xiaoming walks [3a/(3b- 1)-a/b] kilometers every hour.
Solution 3: Let x/2=y/3=k, then x=2k and y=3k.
(7x? -Really? )/(x? -2xy+3y? )
=[7×(2k)? -(3k)? ]/[(2k)? -2×2k×3k+3×(3k)? ]
=(7×4k? -9k? )/(4k? - 12k? +3×9k? )
=(28k? -9k? )/(4k? - 12k? +27k? )
= 19k? / 19k?
= 1