can anyone help with these sums?
Find 1/(1*2) + 1/(2*3) + 1/(3*4) + ... + 1/(99*100).
Find 1/(1*2*3) + 1/(2*3*4) + 1/(3*4*5) + ... + 1/(98*99*100).
+639 (1/1*2)+(1/2*3)+(1/3*4)+(1/4*5)+ .............+(1/99*100) =
= [1/1 - 1/2] + [1/2 - 1/3] + [1/3 - 1/4] + ... + [1/98 - 1/99] + [1/99 - 1/100] = 1/1 - 1/100 = 99/100
:D
+639 (1/1*2)+(1/2*3)+(1/3*4)+(1/4*5)+ .............+(1/99*100) =
= [1/1 - 1/2] + [1/2 - 1/3] + [1/3 - 1/4] + ... + [1/98 - 1/99] + [1/99 - 1/100] = 1/1 - 1/100 = 99/100
:D
