An electric geyser is cylindrical in shape, having a diameter of 35 cm and height 1.2 m. Neglecting the thickness of its walls, calculate

(i) its outer lateral surface area

(ii) its capacity in litres.

(i) Given diameter = 35 cm, height = 1.2 m = 1.2 × 100 = 120 cm.

We know,

radius = $\dfrac{\text{diameter}}{2} = \dfrac{35}{2} = 17.5$ cm.

Curved surface area = 2πrh = $2 \times \dfrac{22}{7} \times 120 \times 17.5 = \dfrac{92400}{7}$ = 13200 cm².

Hence, the outer lateral surface area of electric geyser = 13200 cm².

(ii) Volume of cylinder = πr²h.

Putting values we get,

$\text{Volume of electric geyser } = \dfrac{22}{7} \times (17.5)^2 \times 120 \\[1em] = \dfrac{22 \times 306.25 \times 120}{7} \\[1em] = \dfrac{808500}{7} \\[1em] = 115500 \text{ cm}^3.$

Since 1000 cm³ = 1 litre so, 1 cm³ = $\dfrac{1}{1000}$ litre.

So, Volume = $115500 \times \dfrac{1}{1000}$ litres = 115.5 litres.

Hence, the capacity of electric geyser = 115.5 litres.