Quiz Discussion

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

If a, b, c are in A.P., then (a – c)²/ (b² – ac) =

• 1]

  3

• 2]

  4

• 3]

  1

• 4]

  2

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

• 1] 28
• 2] 87
• 3] 51
• 4] 17

The number of terms of the A.P. 3, 7, 11, 15, ....... to be taken so that the sum is 406 is

• 1]

  5

• 2]

  10

• 3]

  12

• 4]

  14

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]

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

How many terms are there in 20, 25, 30 . . . . . . 140?

• 1] 22
• 2] 25
• 3] 23
• 4] 24

(1) + (1 + 1) + (1 + 1 + 1) + ....... + (1 + 1 + 1 + ...... n - 1 times) = ......

• 1]

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

• 2]

  \(\frac{{n\left( {n - 1} \right)}}{2}\)

• 3]

  \({n^2}\)

• 4]

  n

The sum of the first and third term of an arithmetic progression is 12 and the product of first and second term is 24, then first term is

• 1]

  4

• 2]

  1

• 3]

  8

• 4]

  6

In an A.P., if d = -4, n = 7, an = 4, then a is

• 1] 6
• 2] 7
• 3] 20
• 4] 28

Find the first term of an AP whose 8th and 12th terms are respectively 39 and 59.

• 1] 5
• 2] 6
• 3] 4
• 4] 3
• 5] 7