Basic formula: distance = speed × time; Distance ÷ time = speed; Distance/speed = time
Key question: determine the position in the journey.
Meeting problem: speed sum × meeting time = meeting distance (please write other formulas)
Pursuit problem: Pursuit time = distance difference ÷ speed difference (write other formulas)
Running water problem: downstream travel = (ship speed+water speed) × downstream time = (ship speed-water speed )× downstream time.
Downstream speed = ship speed+current speed = ship speed-current speed.
Still water velocity = (downstream velocity+upstream velocity) ÷2 Water velocity = (downstream velocity-upstream velocity) ÷2
Running water problem: the key is to determine the speed of the object, refer to the above formula.
Bridge crossing problem: the key is to determine the moving distance of the object, refer to the above formula.
For reference only:
Sum and difference problem formula
(sum+difference) ÷2= larger number;
(sum and difference) ÷2= smaller number.
Sum-multiple problem formula
And present (multiple+1)= a multiple;
Multiple x multiple = another number,
Or sum-a multiple = another number.
Formula of differential multiple problems
Difference ÷ (multiple-1)= smaller number;
Smaller number x multiple = larger number,
Or decimal+difference = large number.
Average problem formula
Total quantity/total number of copies = average value.
General travel problem formula
Average speed × time = distance;
Distance/time = average speed;
Distance-average speed = time.
Formula of inverse drawing problem
The problem of reverse travel can be divided into "encounter 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.
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.
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.
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.