Question 1119906
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The area of a trapezoid is (height) times (average of the two bases).  When used in a problem like this to estimate a total, the height of each trapezoid is the length of the time interval; the two bases are the consumption values at the ends of the time interval.<br>
(1) midnight to 1am: 1 hour; average consumption (400+200)/2 = 300 KW/hr; total consumption 300 KW.
(2) 1am to 2am: 1 hour; average consumption (200+350)/2 = 275 KW/hr; total consumption 275 KW.
(3) 2am to 5am: 3 hours; average consumption (350+200)/2 = 275 KW/hr; total consumption 825 KW.
(4) 5am to 6am: 1 hour; average consumption (200+150)/2 = 175 KW/hr; total 175 KW.<br>
Total estimated power consumption: 300+275+825+175 = 1575 KW.