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1)a tank is 30m long 9m wide and 4m deep. what is the cost of plastering its wall and bottom at 25 paise per sq.m?

rs.87

100

90

145

2
by girijithog

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rs.87

100

90

145

by girijithog

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= 2(270 + 36 + 120 )

= 852 sq.m

area of top surface = 30*9 = 270

area of plastering = 852 - 270

= 582

cost of plastering = 25 * 582 = 14550 paise = Rs 145

here, l = 30 m, b = 9m , h = 4 m

2h( l + b) = 2(4) ( 30 + 9)

= 8(39)

=312 m²

area of the base (rectangle) = l × b

= 30 ×9

= 270m²

area of walls and bottom = 312 + 270 = 582 m²

cost of plastering 582 m² = 582× 25

= 14550 paise

= rs.145.50 ( nearly rs. 145)

therefore, the answer is fourth one.