GATE 2022 AR — Architecture – Question 45
A city’s populations in 1981, 1991, 2001, 2011 were 180750, 195850, 215300, 245450. Using 2011 as base and arithmetic growth, project 2041 water demand at 175 litres/person/day. Answer in MLD to two decimal places.
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Correct answer: 53.00 to 56.00
Explanation
The three decadal increases are 15100, 19450 and 30150, averaging 64700/3=21566.6667. Over three more decades, add 64700 to 245450, giving 310150 people. Demand is 310150×175=54276250 litres/day=54.27625 MLD, or 54.28. Arithmetic forecasting adds a constant absolute increase, not a compound percentage.