After 40 minutes into a race, Mark has run ⁸₁₁ of the route while George has covered only ²₁₁ of the distance. Mark runs at the same average speed throughout the race and George’s average speed is 60 m/min slower than Mark’s. If George wants to finish the race at the same time as Mark, by how many percent should he increase his average speed by for the remaining part of the race? Round off your answer to the nearest whole number.
Extra distance that Mark ran more than George in first 40 min
= 40 x 60
= 2400 m

Fraction of the entire distance that was covered by Mark more than George in the first 40 min
= ⁸₁₁ - ²₁₁
= ⁶₁₁

⁶₁₁ of the entire distance = 2400 m
¹₁₁ of the entire distance = 2400 ÷ 6 = 400 m

Distance that George ran in the first 40 min
= 2 x 400
= 800 m

George's average speed
= 800 ÷ 40
= 20 m/min

Mark's average speed
= 20 + 60
= 80 m/min

Fraction of the journey that Mark needed to run to complete the race
= 1 - ⁸₁₁
= ³₁₁

¹₁₁ of the entire distance = 400 m
³₁₁ of the entire distance = 3 x 400 = 1200 m

Duration that Mark would take to complete
= 1200 ÷ 80
= 15 min

Fraction of the journey that Mark needed to run to complete the race
= 1 - ²₁₁
= ⁹₁₁

⁹₁₁ of the entire distance = 9 x 400 = 3600 m  

Speed that George needs to take to complete distance at the same time as Mark
= 3600 ÷ 15
= 240 m/min

Increase in George's average speed
= 240 - 20
= 220 m/min

Percentage increase in George's average speed
= ²²⁰₂₀ x 100%
≈ 1100%

Answer(s): 1100%