Q50 / 57 · KVPY 2019 (SA) · Physics

Mumbai needs 1.4×1012 L of water annually. Its effective surface area is 600 km2 and it receives an average rainfall of 2.4 m annually. If 10% of this rain water is conserved, it will meet approximately

  • A
    1% of Mumbai's water needs
  • Correct answer
    B
    10% of Mumbai's water needs
  • C
    50% of Mumbai's water needs
  • D
    100% of Mumbai's water needs

Solution

Surface area over which rain is
A=600 km2

=600×1032 m2

=6×108 m2

Average rainfall, h=2.4 m Volume of water received by rain, V
=A×h=6×108×2.4 m3

Water conserved =10% of volume received by rain =6×108×10100×2.4 m3=1.44×108 m3

=1.4×108×103 L=1.4×1011 L
Percentage of total water consumption received by rain is
=1.4×1011×1001.4×1012=10%

Hence, the correct answer is option: 'B'.

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