Question

the radius and height of a cylinder are equal find the total surface area if the curved surface area of cylinder is 628cm square (curved surface area =2Pie rh,total surface area =2pie r(r+h) )​

Answer 1

we know that the height is twice the radius .

h=2r

the formula of c.s.a =2πrh

we substitute height from radius

we prove h=2r

so , the formula is 2πrh

2πr2r

c.s.a=628cm2

so,the c.s.a is 2πr2r

2πr2r = 628

2×22/7×2r2 =628

44/7×2r2 =628

44×2r2=628×7

44×2r2=4396

2r2=4396/44

2r2=99.9090

r2=99.9090/2

r2=49.9545

r=√49.9545

r=7.067

so,the height of the cylinder is 2r

r=7.067

2r

2×7.067

14.134

The T.S.A.=2πr(r+h)

2×22/7×7.067(7.067+14.134)

44/7×7.067(21.201)

310.948/7×21.201

6592.40855/7

941.77265