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1. If x, y, z are three sums of money such that y is the simple interest on x and z is the simple interest on y for same time and at the same rate of interest, then we have

y^{2} = zx

z^{2} = xy

xyz = 1

x^{2} = yz

2. A and B can together finish a working 30 days. They worked together for 20 days and then B left. After another 20 days, A finished the remaining work. The number of days in which B alone can finish the work is

60

50

48

54

3. If 6x - 5 y = 13, 7x + 2y = 23, then 11x + 18y =

15

-15

51

33

4. If x + y + z = 13 and x^{2} + y^{2} + z^{2} = 69 , then the value of xy + z(x+ y) is equal to

70

40

5. Two trains, of same length, are running in parallel tracks in the same direction with speed 60 km/hour and 90 km/hour respectively. The latter completely crosses the former in 30 seconds. The length of each train (in metres) is

115

125

150

100