Quiz Discussion

Sum of n terms of the series $\sqrt 2   +   \sqrt 8   +   \sqrt {18}   +   \sqrt {32}   +$ ....... is

• 1]

  $\frac{{n\left( {n + 1} \right)}}{2}$

• 2]

  $2n\left( {n + 1} \right)$

• 3]

  $\frac{{n\left( {n + 1} \right)}}{{\sqrt 2 }}$

• 4]

  1

If an A.P. has a = 1, tn = 20 and sn = 399, then value of n is :

• 1] 20
• 2] 32
• 3] 38
• 4] 40

Let S denotes the sum of n terms of an A.P. whose first term is a. If the common difference d is given by d = S_n – k S_n-1 + S_n-2 then k =

• 1]

  1

• 2]

  2

• 3]

  3

• 4]

  4

How many terms are there in the GP 5, 20, 80, 320........... 20480?

• 1] 5
• 2] 6
• 3] 8
• 4] 9
• 5] 7

The 2nd and 8th term of an arithmetic progression are 17 and -1 respectively. What is the 14th term?

• 1] -22
• 2] -25
• 3] -19
• 4] -28