Question

4. How many cubic
metre of earth must be dug out to make a well 28m deep and 2.8m in diameter ? Also, find the cost of plastering it's inner surface at * 4.50 per sq. metre.​

Answer 1

ANSWER :

d=2.8 ,r=1.4m

h=28m

the volume of a cylinder = πr^h

=22/7*1.4*1.4*28

=172.48m^

the cost of painting

1m^ = 4.50rs.

172.48m^ = ?

172.48*4.50 = 776.16

therefore the cost of painting inner surface is 776.16rs.

Answer 2

$volume \: of \: well = \pi \: r ^{2} h \\ = 22 \div 7 \times (1.4) {}^{2} \times 28 \\ = 172.48m {}^{3}$

$area \: of \: plastering = 2\pi \: r \: h \\ = 2 \times 22 \div 7 \times 1.4 \times 28 \\ = 246.4m {}^{2}$

$cost \: for \: plastering \: = 246.4 \times 4.5 \\ = 1108.8rupees$

therefore the money cost for plastering is Rs 1108.8

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