1. The diagonal diameter of the circle inscribed with the rectangle is 40 cm. According to Pythagorean theorem, the length is twice the width, and it can be calculated that the length is 16 times the root sign and the width is 8 times the root sign.

This is a right triangle, the hypotenuse is 6m, and the right is 2m. The problem of finding another right-angled edge. According to Pythagorean theorem, the opponent is more than 5.6 meters. Achievable

Is your oil drum horizontal or vertical? I can't answer without a clear explanation.

4. First, factorize to get (a? +b？ -3)(a？ +b？ +2)=0

Get an a? +b？ =3 or a? +b？ =-2 (give up)