Question

28. The height of a cylinder whose radius is 7 cm

and the total surface area is 968 cm2 is.............
(A) 15 cm
(C) 19 cm
(B) 17 cm
(D) 21 cm

Answer 1

`\huge\bold{Solution }`

`\large\mathfrak{given}`

• TSA = 968cm²
• Radius = 7 cm
• Height = ?

`\large \: \mathfrak{ {formula}}`

• 2πr(r + h)

Let height be : x

`\sf\Rightarrow{ \: 968 = 2\pi \: r(r \: + h) } \:`

`\sf\Rightarrow{968 = 2 * (22)/(7) * 7 * (7 + x) }`

`\sf\Rightarrow{ 968 = 2 * 22 *(7 + x)}`

`\sf\Rightarrow{ 968 = 44(7 + x)}`

`\sf\Rightarrow{ (968)/(44) = 7 + x}`

`\sf\Rightarrow{22 = 7 + x }`

`\sf\Rightarrow{22 - 7 = x }`

`\sf\Rightarrow{x = 15 }`

`\bf\Rightarrow{ x = 15}`

`\sf\Rightarrow{ \underline{{ height \: = 15}}} \\ \\ \sf \: option \: A is \: correct \:`

`{\underline{ \rule {200pt}{6pt}}}`