(sum and difference) ÷2= smaller number.

2. The formula of the sum-times problem

And present (multiple+1)= a multiple;

Multiple x multiple = another number,

Or sum-a multiple = another number.

3. Formula of differential multiple problems

Difference ÷ (multiple-1)= smaller number;

Smaller number x multiple = larger number,

Or decimal+difference = large number.

4, the average problem formula

Total quantity/total number of copies = average value.

5. Formula of general travel problem

Average speed × time = distance;

Distance/time = average speed;

Distance-average speed = time.

6. Formula of inverse stroke 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.

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).

10, engineering problem formula

(1) general formula:

Efficiency × working hours = total workload;

Total workload ÷ working time = working efficiency;

Total amount of work ÷ efficiency = working hours.

(2) Assuming that the total workload is "1", the formula for solving engineering problems is:

1÷ working time = the fraction of the total amount of work completed in unit time;

1What is the score that can be completed per unit time = working time.

1 1, profit and loss problem formula

(1) A surplus (surplus) and a deficit (deficit), the formula can be used:

(surplus+deficit) ÷ (the difference between two distributions per person) = number of people.

(Excerpt for reference)