Question

find the cost of plastering in the inner surface of the wall at rupees 9.50 per metre square is 21 m Deep and it has a diameter of its top is 6 metre​

Answer 1

Answer:

Rs. 3762

Step-by-step explanation:

Inner surface of well = πdh

d = diameter of well = 6m

h = height of well = 21m

Calculating inner surface area from above formula

we get Inner Surface = 22 * 6 * 21 / 7 = 396 square meter

Cost of plastering per square meter = Rs. 9.5

Total cost of plastering inner surface = inner surface area * cost per meter square

= 396 * 9.5 = Rs. 3762

Answer 2

if shape of well = shape of cylindrical tank

diameter = 6 m , radius = 6/2 = 3m

depth of well h = 21m

then,

area of the inner surface of well

= CSA of well + area of lower circular end of well

= 2πrh + πr^2 = πr( 2h + r)

= 22×3/7 ( 2×21 + 3 )

= 66 × 45/ 7 = 2970/ 7 m^2

cost of 1 m^2 = ₹9.50

cost of plastering inner surface area of the well = 9.50 × 2970/7

= ₹4030.7

second case:

it often seen that lower part of well remains unplastered so thus there is no need to plaster lower end of well. in that case

inner surface area

= 2πrh

= 2×22 × 3 × 21/ 7

= 396m^2

cost of 1 m^2 = ₹9.50

cost of plastering the inner surface of well = 9.50 × 396 = ₹3762

Answer:₹3762