Average speed × time = distance;

Distance/time = average speed;

Distance-average speed = time.

6. Formula of reverse travel problem The reverse travel problem can be divided into two types: "meeting problem" (two people start from two places and walk in opposite directions) and "separation problem" (two people walk with their backs to each other). Both of these problems can be solved by the following formula:

(speed sum) × meeting (leaving) time = meeting (leaving) distance;

Meet (leave) distance ÷ (speed sum) = meet (leave) time;

Meet (leave) distance-meet (leave) time = speed and.

7. Formula of the problem of traveling in the same direction.

Catch-up (pull-out) distance ÷ (speed difference) = catch-up (pull-out) time;

Catch up (pull away) the distance; Catch-up (pull-away) time = speed difference;

(speed difference) × catching (pulling) time = catching (pulling) distance.

8. Formula of train crossing bridge problem

(bridge length+conductor) ÷ speed = crossing time;

(Bridge length+conductor) ÷ Crossing time = speed;

Speed × crossing time = sum of bridge and vehicle length.

9, navigation problem formula

(1) general formula:

Still water speed (ship speed)+current speed (water speed) = downstream speed;

Ship speed-water speed = water flow speed;

(downstream speed+upstream speed) ÷2= ship speed;

(downstream speed-upstream speed) ÷2= water flow speed.

(2) Formula for two ships sailing in opposite directions:

Downstream speed of ship A+downstream speed of ship B = still water speed of ship A+still water speed of ship B.

(3) Formula for two ships sailing in the same direction:

Hydrostatic speed of rear (front) ship-Hydrostatic speed of front (rear) ship = the speed of narrowing (expanding) the distance between two ships.

(Find out the speed of narrowing or widening the distance between the two ships, and then solve it according to the relevant formula above).