Question

1,-2,3,-4,5...........what is the averageof first 200 numbers

Answer 1

1, -2, 3, -4, 5, .... 200  

1 - 2 + 3 - ... + 200  

= (1 + 3 + 5 + .... + 199) - (2 + 4 + 6 + ... + 200)  

= 50*200 - 50*202  

= 10000 - 10100  

= -100  

The average of the sequence is -0.5