71) One train 60 meters long is running with a speed of 20 km per hour. It passes from a bridge of 90 meters long. What time will be taken by the train to pass from bridge?

72) In the metal conduit system of wiring where there is a zigzag wall protection, the cables can be run by using

73) ON plotting the graph A(1,0), B(3,0), C(4,4), D(1,4) and joining AB, BC, CD and DA, which of the following figures is obtained?

74) From the point P(-6,6), the perpendiculars drawn meet the x-axis and y-axis at points M and N respectively. The coordinates of the points M and N are

75) How much quantity of heat is needed to change the temperature of 300 gm of copper from 25 degree centigrade to 75 degree centigrade? (Specific heat of copper is 0.092 cal/gm degree centigrade)