Q 1 :

In an A.P., if the first term a = 7, nth term an 84 and the sum of first n terms Sn = 2093/2, then n is equal to:

  • 22

     

  • 24

     

  • 23

     

  • 26

     

(3)

Sn=n2(a+an)20932=n2(7+84)

91n=2093n=23

 



Q 2 :

Which term of the A.P. –29, –26, –23, ..., 61 is 16?

  • 11th

     

  • 16th

     

  • 10th

     

  • 31st

     

(2)

Given, a=-29

d=-26-(-29)=-26+29=3d=3

an=16

Here we know, an=a+(n-1)d

16=-29+(n-1)3

16+29=(n-1)3=15

n-1=453=15

15=n-1n=16



Q 3 :

The 7th term from the end of the A.P. : – 8, – 5, – 2, ..., 49 is :

  • 67

     

  • 13

     

  • 31

     

  • 10

     

(3)     31

 



Q 4 :

If k + 7, 2k – 2 and 2k + 6 are three consecutive terms of an A.P., then the value of k is :

  • 15

     

  • 17

     

  • 5

     

  • 1

     

(2)         17

 



Q 5 :

The common difference of an A.P. in which a15 – a11 = 48, is

  • 12

     

  • 16

     

  • –12

     

  • –16

     

(1)

a15-a11=48

a+14d-a-10d=48

4d=48d=12



Q 6 :

The next (4th) term of the AP 18, 50, 98,  is:

  • 128

     

  • 140

     

  • 162

     

  • 200

     

(3)

We have,18 = 9×2 = 3250 = 25×2 = 52and98 = 49×2 = 7232, 52, 72,  are in AP where a = 32 and d = 72  52 = 22Thus, 4ʰ term = 32 + (4  1)×22= 32 + 62 = 92 = (9)²×2 = 162Option (c) is correct.



Q 7 :

The nth term of an AP is 7n+4. The common difference is:

  • 7n

     

  • 4

     

  • 7

     

  • 1

     

(3)

We have,an=7n+4an-1=7(n-1)+4=7n-3 Common difference,d=an-an-1=(7n+4)-(7n-3)=7



Q 8 :

The common difference of the AP 12x,1-4x2x,1-8x2x, is:

  • −2x

     

  • −2

     

  • 2

     

  • 2x

     

(2)

Given AP is12x,1-4x2x,1-8x2x, Common differenced=1-4x2x-12x=1-4x-12x=-4x2x=-2

 



Q 9 :

If a, b, c from an AP with common difference d, then the value of a-2b-c is equal to

  • 2a+4d

     

  • 0

     

  • -2a-4d

     

  • -2a-3d

     

(3)

a,b,care in AP with common difference =d b-a=c-b=db-a=da=b-db=a+dand c-b=dc=b+dc=a+2dNow,a-2 b-c=a-2(a+d)-(a+2d)=a-2a-2d-a-2d=-2a-4d

 



Q 10 :

The 11th term from the end of the AP: 10, 7, 4, …, –62 is

  • 25

     

  • 16

     

  • -32

     

  • 0

     

(3)

Given AP is 10, 7, 4, …, –62.

nthterm from end=l-(n-1)d

Here,l=-62, d=7-10=-3

11thterm from end =-62-(11-1)(-3)=-62+30=-32