GATE 2017 CE (CE2) – Question 57
A 25 km × 25 km catchment has four rain gauges at its corners and one at its centre, as shown. Rainfall at G1, G2, G3, G4 and G5 is 300, 285, 272, 290 and 288 mm respectively. The Thiessen-polygon average, to one decimal place, is ______ mm.
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Correct answer: 286.9 to 287.9
Explanation
Thiessen bisectors assign the centre gauge half the catchment and each corner one eighth. Therefore $\bar P=(300+285+272+290)/8+288/2=287.375$ mm, or 287.4 mm. The unequal weights rule out a simple five-gauge mean.