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Volumes Practice Test 3

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Question : 8 of 40

Marks: +1, -0

A cistern 6m long and 4m wide, contains water upto a depth of 1m 25cm. Find the total area of the wet surface.

49 $m^2$
50 $m^2$
53.5 $m^2$
55 $m^2$

Solution:

Concept:

The wet surface area includes the base of the cistern and the four vertical walls up to the water depth.

Explanation:

Length

l = 6\,\mathrm{m}

, width

b = 4\,\mathrm{m}

, water depth

h = 1\,\mathrm{m}\,25\,\mathrm{cm} = 1.25\,\mathrm{m}

.

Base area

= l \times b = 6 \times 4 = 24\,\mathrm{m}^2

.

Area of two longer walls

= 2 \times l \times h = 2 \times 6 \times 1.25 = 15\,\mathrm{m}^2

.

Area of two shorter walls

= 2 \times b \times h = 2 \times 4 \times 1.25 = 10\,\mathrm{m}^2

.

Total wet surface area

= 24 + 15 + 10 = 49\,\mathrm{m}^2

.

Answer:

49\,\mathrm{m}^2

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