Cylinder problem: Determine the restriction on the hight

[wind]

A cylindrical frame consisting of three circles and four vertical supports is built from 6m of wire, as shown. The frame is then covered with paper to form a closed cylinder. Determine an expression for the radius r in terms of the height h.

3pi r^2 + 4h = 6
3pi r^2 ÷ 3pi = 6 - 4h ÷ 3pi
r^2 = 6 - 4h ÷ 3pi
r = root 6 - 4h ÷ 3pi

But this answer is wrong. Can someone point out where I went wrong? Thanks

 

[TchrWill]

Re: Cylender wordproblem-Determine expression for r in tems

A cylindrical frame consisting of three circles and four vertical supports is built from 6m of wire, as shown. The frame is then covered with paper to form a closed cylinder. Determine an expression for the radius r in terms of the height h.

3pi r^2 + 4h = 6
3pi r^2 ÷ 3pi = 6 - 4h ÷ 3pi
r^2 = 6 - 4h ÷ 3pi
r = root 6 - 4h ÷ 3pi

But this answer is wrong. Can someone point out where I went wrong? Thanks

You used the area of the circles instead of the circumference.

3(2r)Pi + 4h = 6 should get you your answer.

 

[wind]

^ thank you, i got it

 

[wind]

I have another question

determine the restriction on the height if the radious of the cylendar must be atleast 10.

10 > 3- 2h/3pi

3pi(10)> 3- 2h

30pi-3 > -2h

(30pi - 3)/-2 < h

I don't think I'm doing this right, can someone help me? Thanks