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Answer:
150 minutes
Step-by-step explanation:
Volume of prism = height * base area
Height of prism = 1m
Base area = area of a trapezium
Area of trapezium = 0.5(a + b) h
a, b = parallel sides, h= height of trapezium
Area of trapezium = 0.5(1.4+0.6)*2
Area = 0.5(2)*2 = 2m²
Hence,
V of prism = area of trapezium * height of prism
Volume = 2m² * 1m = 2m³
Decrease in water level due to pumping
20cm decrease in 30minutes
(20/100)m in 30 minutes
0.2 m decrease in height of water
Hence, height of water in prism after 30 minutes pumping :
height - 0.2 = 1 - 0.2 = 0.8m
Volume after 30 minutes of pumping :
Base area * new height
2m² * 0.8m = 1.6m³
Decrease in volume over 30 minutes :
(Initial volume - volume after pumping)
2m³ - 1.6m³ = 0.4m³
If ;
0.4m³ = 30 minutes
1.6m³ = x
0.4x = 48
x = 48 / 0.4
x = 120
Hence, it takes 120 minutes for the remaining 1.6m³ to be emptied.
Hence, total wait time :
120 minutes + 30 minutes
= 150 minutes
