1. After improving efficiency, it is 45 words per minute, and the formula is 30*( 1+50%)=45. Suppose this material has a word.

So (a divided by 30)-(3a divided by 45)-(2a divided by 30)=20, and a=3000 is obtained.

2. Assuming that one product is produced every month, if the scheme 1 is selected, the sewage charge is 0.5a*2+30000, and the profit at this time is 50a-(0.5a*2+30000)-25a. If the second scheme is selected, the sewage charge is 0.5a* 14, and the profit at this time is 50a-(0.5A * 14). If the profit is 2 (copy the formula by yourself), you can get one & gt5000 pieces, so if the factory produces less than 5000 pieces per month, choose scheme 2, and if it exceeds 5000 pieces, choose scheme 1.

3 If the number of air passengers is x million, the number of sea passengers is (500-x) million, 4x+(500-x)*22=2900. The result is x = 45,000.

So 4.5 million people are transported by air and 500,000 by sea.

4 can be converted into minutes first, so the speed of A is 500/6 meters per minute, and the speed of B is 1300/6 meters per minute, so the time for B to catch up with A is t minutes, and the formula is (500/6) *16+(500/6) * t = (650).

(Note: A and T used in the above solution can be replaced by X)