Project ForgeIn a graph, the concentration of a particular pollutant in a lake is plotted over (alternate) days of a month in winter (average temperature 10C) and a month in summer (average temperature 30C). Winter concentration rises from about 0 ppm (day 0) to about 8 ppm (day 30). Summer concentration rises from about 1.5 ppm (day 0) to about 10.5 ppm (day 30), with the two curves crossing/nearly overlapping around days 8-14.
Consider the following statements based on this data: i. Over the given months, the difference between the maximum and the minimum pollutant concentrations is the same in both winter and summer. ii. There are at least four days in the summer month such that the pollutant concentrations on those days are within 1 ppm of the pollutant concentrations on the corresponding days in the winter month.
Which one of the following options is correct?
- AOnly i
- Only ii
- CBoth i and ii
- DNeither i nor ii
Explanation
Winter's range is about 8-0=8 ppm, while summer's range is about 10.5-1.5=9 ppm — these are NOT the same, so statement (i) is FALSE. Around days 8-14, the two curves cross and run very close together (within about 1 ppm of each other) across several consecutive plotted days, satisfying 'at least four days' — so statement (ii) is TRUE. Only (ii) is correct.
Source: GATE ME 2017 Session 2 (ME-2) (2017)
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