Question

The total surface area of a cylinder is 880 cm. It's height is 13 cm. Find it's
radius.
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Answer 1

total suface area =880 cm^2

height= 13cm

radius= ?

formula=2πr(r+h)

880 = 2*22/7*r(r+13)

880/2*7/22 = r (r+13)

440*7/22 = r(r+13)

20*7 = r(r+13)

140=r(r+13)

hope this can help uu

Answer 2

$TSA = 2 \pi r (r+h)\\ \\ \Rightarrow 880 = 2 \times \frac{22}{7} \times r (r+13)\\ \\ \Rightarrow \frac{880 \times 7}{2 \times 22} = r^2 + 13r\\ \\ \Rightarrow 140 = r^2 + 13r\\ \\ \Rightarrow r^2 +13r - 140 = 0\\ \\ \Rightarrow r^2 + 20r -7r -140 = 0 \\ \\ \Rightarrow r(r+20)-7(r+20)=0\\ \\ \Rightarrow(r+20)(r-7)=0\\ \\ \Rightarrow r = 7, -20\\ \\ \text{Since radius can not be negative, radius = 7 cm}$