1) Let the radius of the cone be r and the height be h 1. The radius of the cylinder is 3/4R and the height is h2. rule

1/3R？ ×π×h 1/(3/4R)？ ×π×h2=2/3

The solution is h 1/h2=32/9.

2) I won't

3) A 3x，B 4x

4x 70+3x 90-(4+3)x 70 = 1800

X=30

Then 3x+4x=420 (person)