the total surface area ofa cylinder, A, is given by the formula
A=2πr2+2πrh
Given that A=200cm^2 and h=10, find the value of r

Question

the total surface area ofa cylinder, A, is given by the formula 
A=2πr2+2πrh
Given that A=200cm^2 and h=10, find the value of r

anonymous · Answer

the equation is:
$$A= 2\pi r ^{2} + 2\pi rh$$

unklerhaukus · Answer

can you  solve the equation for r?

jack1 · Answer

hint: 
y = ax^2 + bx + c = 0

anonymous · Answer

r=Ahr^2/2pi

anonymous · Answer

ii don;t think that's right though....

jack1 · Answer

hmm... what i would do is make the whole equation = 0
so A = 200
h = 10
it's already in the form of a quadratic (ax^2 + bx + c )
so 
if A=2πr^2+2πrh
200 = 2πr^2+2πr10
0  = 2πr^2+20πr - 200 
y =  ax^2 + bx + c

now solve using quadratic formula

jack1 · Answer

is that all making sense @n9767 ?

jack1 · Answer

did u need this at all (for reference)?

anonymous · Answer

oh sorry my computer's really slow!
THank uou SOO much!!! i understand now!!

jack1 · Answer

all good, y w, what'd jew get for ur answer (just out of curiosity)?

anonymous · Answer

i got 2.5 cm

anonymous · Answer

is it right?

jack1 · Answer

yep, i got 2.54