Saved Bookmarks
| 1. |
A field is in the shape of a trapezium having parallel sides 90 m and30 m. These sides meet the third side at right angles. The length of thefourth side is 100 m. If it costs 5 to plough 1 m2 of the field, find thetotal cost of ploughing the field. |
|
Answer» Given Parallel sides of trapezium= 90 m and 30 m,So ,Let AB = 90 m ,CD = 30 mAndAB | | CD And these sides meet third side at right angles , So let third side = ADAndLength of fourth side ( BC ) = 100 m Now we draw a perpendicular from point C at AB that meet AB at E , SOHeight of Trapezium ABCD = AD = ECAndAE = CD = 30 m So,BE = AB - AE = 90 - 30 = 60 m Now we apply Pythagoras theorem in∆BEC , As : BC²= BE²+ EC² 100²= 60²+ EC² EC²= 10000 - 3600 EC²= 6400 EC = 80 m ( This also height of trapezium field ) We know Area of Trapezium = 12( Sum of parallel sides )×( Height )So,Area of Trapezium ABCD =12( 90 + 30 )×( 80 ) Area of TrapeziumABCD=120×40 Area of TrapeziumABCD= 4800 m² And ,costs Rs 4 to plough 1m² of the field . Total cost to plough the whole field = 4800× 5 = Rs. 24000 |
|