Length a, width b and height h.

B=3h, and b+h=a (that is, a=4h).

The increased surface area is 2ab+2bc, which means 2ab+2bc=200.

Find the volume abh and get 160√ 15/3.

2.

Let the amount of money per loaf of bread be x, and each loaf of bread should be 8x/3.

C 4 yuan should be paid, that is, 8x/3=4 and x=3/2.

A The money that should be recovered is 5x-8x/3=7/3x=7/2=3.5 yuan.

3.

Let the number of male teachers be m and the number of female teachers be n.

According to the meaning of the question, (50m+35n)/(m+n)=40. Solution, 2m=n

Male teacher: female teacher = 1:2

4.

Let * * * have x parts, and it takes n days for master and apprentice to process at the same time.

Then the master processes x/9 parts every day, and the apprentice processes x/ 15 parts every day.

N=x/(x/9+x/ 15), then n=45/8.

After the completion, the master made 100 more parts than the apprentice, that is, n (x/9)-n (x/15) =100, and substituted n=45/8.

X=400, and * * * has 400 parts.

5.

Assume that the passenger car speed is 7v and the freight car speed is 5v.

According to the meaning, 3*7v=3*5v+50, and v=50/6.

Then the distance between the two places is 2 * (3 * 7V) = 350km.