If in a series tn = n/(n+1), Then Σ tn; n=1,20 is equal to

Question

If in a series \(t_n= \frac n{(n + 1)}\), Then \(\sum\limits_{n =1}^{20}t_n\) is equal to

a. \(\frac{20! -1}{20!}\)

b. \(\frac{21! -1}{21!}\)

c. \(\frac1{2(n -1)!}\)

d. none of these

Answer 1

Correct option is b. \(\frac{21! -1}{21!}\)