Quiz Discussion

Find the nth term of the following sequence :

• 1]

  5(10n - 1)

• 2]

  5n(10n - 1)

• 3]

  \(\frac{5}{9} \times \left( {{{10}^n} - 1} \right)\)

• 4]

  \({\left( {\frac{5}{9}} \right)^n} \times \left( {{{10}^n} - 1} \right)\)

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

The 3^rd and 7^th term of an arithmetic progression are -9 and 11 respectively. What is the 15^th term?

• 1]

  28

• 2]

  87

• 3]

  51

• 4]

  17

What is the sum of the first 11 terms of an arithmetic progression if the 3rd term is -1 and the 8th term is 19?

• 1] 204
• 2] 121
• 3] 225
• 4] 104

A boy agrees to work at the rate of one rupee on the first day, two rupees on the second day, and four rupees on third day and so on. How much will the boy get if he started working on the 1st of February and finishes on the 20th of February?

• 1] 220
• 2] 220 -1
• 3] 219 -1
• 4] 219
• 5] None of these

Consider an infinite G.P. with first term a and common ratio r, its sum is 4 and the second term is 3/4, then

• 1]

  a = 7/4, r = 3/7

• 2]

  a = 2, r = 3/8

• 3]

  a = 3, r = 1/4

• 4]

  a = 3/2, r = ½

Which term of the A.P. 24, 21, 18, ............ is the first negative term?

• 1] 8th
• 2] 9th
• 3] 10th
• 4] 12th

The sum of first five multiples of 3 is:

• 1] 45
• 2] 65
• 3] 75
• 4] 90

The first and last term of an A.P. is a and l respectively. If S is the sum of all the terms of the A.P. and the common difference is given by \(\frac{{{l^2} - {a^2}}}{{k - \left( {l + a} \right)}}\)   then k = ?

• 1] S
• 2] 2S
• 3] 3S
• 4] None of these

If Sn denote the sum of the first n terms of an A.P. If S2n = 3Sn , then S3n : Sn is equal to

• 1] 4
• 2] 6
• 3] 8
• 4] 10