A field is in the shape of a trapezium having parallel sides 90 m and 30 m. These sides meet the third side at right angles. The length of the fourth side is 100 m. If it costs Rs 4 to plough 1m2 of the field, find the total cost of ploughing the field.



PQ = 90m


RS = 30m


QR = 100m


PQ = PT + TQ = 90m


30 + TQ = 90


TQ = 60


In ΔTRQ,


QR2 = TR2 + QT2


1002 = TR2 + 602


TR2 = 10000-3600


TR2 = 6400


TR = 80m


Area (PQRS) =


Area(PQRS) =


Area(PQRS) = 60 × 80 = 4800 m2


Cost of ploughing = Area(PQRS) × Cost per m2


Cost of ploughing = 4800 × 4 = Rs. 19200.


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