In the 100 meter race between a and B, when a reaches the finish line, B is still 10 meters away from the finish line. If a retreats 10 meters from the starting point, who will reach the finish line first?

In the 100 meter race between a and B, when a reaches the finish line, B is still 10 meters away from the finish line. If a retreats 10 meters from the starting point, who will reach the finish line first?

Let the time used be X
A speed = 100 / x B speed = 90 / X
For the second time, the first time is 110 / (100 / x) = 110x / 100
B time = 100 / (90 / x) = 100x / 90
So 110x / 100 is less than 100x / 90
So a comes to the end first

Party A and Party B conduct the "100 meter race". When Party A reaches the finish line, Party B is still 10 meters away from the finish line: (1) if Party A is allowed to retreat 10 meters from the starting line, Party A and Party B start at the same time______ (2) to make Party A and Party B start at the same time and reach the terminal at the same time, Party B should move forward from the starting line______ m．

A is faster than B. If a goes back 10 meters from the starting line and runs with B at the same time, then a runs 100 meters and B just runs 90 meters. At this time, they meet and are 10 meters away from the finish line. This is equivalent to letting them start the race at the same time 10 meters away from the finish line. A is faster, so he reaches the finish line first, At the same time, B should move 10 meters forward from the starting line, so that a runs 100 meters, B just runs 90 meters

Party A and Party B run the 100 meter race. When Party A reaches the finish line, Party B is still 10 meters short. If Party A retreats 10 meters from the starting point, they still run at the same speed
At the same time to the end

Wrong
Let a arrive first. Let a's speed be x and B's speed be y. let 100 / x = 90 / y have x = 10 / 9y. If x = 10 / 9y is substituted by 110 / x, 110 / x = 99 / y will be obtained, which is smaller than 100 / y, that is, it takes less time, so a is faster

A and B start running from the same starting point on the 400 meter circular track. A runs faster than B. if they run in the same direction, they meet each other every 3 minutes and 20 seconds,
Let a be XM / s, then B be XM / s_____ M / s, what is the equivalent relationship when they run in reverse____

Let a be XM / s, then B be XM / s_ (x＋2)_ M / s, what is the equivalent relationship when they run in reverse
_ Equal time_
(V A-V b) × 200 = 400
(X-V b) × 200 = 400
So v b = x + 2