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# NCERT Solutions for Class 10 Maths Exercise 5.3 Chapter 5 Arithmetic Progression

NCERT Solutions for Class 10 Maths Exercise 5.3 of Chapter 5 Arithmetic Progression are introduced here by Future Study Point for helping class 10 maths students of CBSE to help their groundwork preparations for the class 10 CBSE Board exam Term 2. NCERT Solutions for Class 10 Maths Exercise 5.3 Chapter 5 Arithmetic Progression are the best review inputs for clearing the ideas on Arithmetic Progression. The questions on Arithmetic Progression are based on our day-to-day existence issues on various sorts of points where we really want to predict actual amounts of physical quantity which are ordered in a sequence. All NCERT Solutions for Class 10 Maths Exercise 5.3 Chapter 5 Arithmetic Progression are made here by an accomplished CBSE Maths instructor by a bit by bit strategy according to the standards of CBSE, in this manner, class 10 maths students can undoubtedly comprehend the solutions.

## NCERT Solutions for Class 10 Maths Exercise 5.3 Chapter 5 Arithmetic Progression

Q1.Find the sum of the following APs.

(i) 2, 7, 12 ,…., to 10 terms.
(ii) – 37, -33, -29 ,…, to 12 terms
(iii) 0.6, 1.7, 2.8 ,…….., to 100 terms
(iv) 1/15, 1/12, 1/10, …… , to 11 terms

Ans. (i) The given AP is 2, 7, 12 ,…., to 10 terms.

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

Where n = 10, first term,a = 2, common difference,d = 7 -2 = 5

S10= 10/2[2×2 + (10 – 1)d]

S10= 5[4 + 9×5]= 5(4 +45) =5×49 =245

(ii) The given AP is – 37, -33, -29 ,…, to 12 terms

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

Where n = 12, first term,a = -37, common difference,d = -33 +37 = 4

S10= 12/2[2×-37 + (12 – 1)×4]

S10= 6[-74 + 11×4]= 6(-74 +44) =6×-30 =-180

(iii) The given AP is 0.6, 1.7, 2.8 ,…….., to 100 terms

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

Where n = 100, first term,a = 0.6, common difference,d = 1.7 -0.6 = 1.1

S10= 100/2[2×0.6 + (100 – 1)×1.1]

S10= 50[1.2 + 99×1.1]= 50(1.2 +108.9) =50×110.1 =5505

(iv) The given AP is 1/15, 1/12, 1/10, …… , to 11 terms

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

Where n = 11, first term,a = 1/15, common difference,d =1/12 -1/15= (5-4)/60 =1/60

S11= 11/2[2×1/15 + (11 – 1)×1/60]

S10= 11/2[2/15 + 10/60]= 11/2(2/15 +1/6) =11/2(4+5)/30) =(11×9)/60=99/60 =33/20

Hence the sum of 11 terms of the given AP is 33/20

Q2.Find the sums given below:

(ii) 34 + 32 + 30 + ……….. + 10
(iii) – 5 + (− 8) + (- 11) + ………… + (- 230)

Ans. The given AP is

Where a = 7,

nth term of a AP is given by

an= a + (n -1)d

7 +(n -1)×7/2 = 84

(n -1)×7/2 = 84 – 7 = 77

n -1 = 77×2/7 =22

n = 23

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

= 23/2[2×7 + (23 – 1)×7/2]

= 23/2[14 + 22×7/2]

= 23/2[14 + 77]

= 23/2 ×91

=2093/2

(ii)The given AP is  34 + 32 + 30 + ……….. + 10

nth term of a AP is given by

an= a + (n -1)d

Where a = 34, d = 32 – 34 = -2 and an=10

34 +(n -1)×-2 = 10

-2n + 2 = 10 – 34 = -24

-2n = -26

n = 13

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

= 13/2[2×34 + (13 – 1)×-2]

= 13/2[68 -12×2]

=13/2[68 -24]

=13/2×44

=13× 22 =286

Hence sum of the given AP is 286

(iii) The given AP is  – 5 + (− 8) + (- 11) + ………… + (- 230)

nth term of a AP is given by

an= a + (n -1)d

Where a = -5, d = -8 +5= -3 and an=-230

-230= -5 + (n -1)×-3

(n -1)×-3 = -235+5 =-225

n -1 = -225/-3 = 75

n = 75+1 =76

The sum of n terms of the AP is given by

Sn= 76/2[2×-5 + (76 – 1)×-3]

= 76/2[-10 + 75×-3]

= 76/2[-10-225]= 38×-235=-8930

Sn=-8930

Q3.In an AP
(i) Given a = 5, d = 3, an = 50, find n and Sn.
(ii) Given a = 7, a13 = 35, find d and S13.
(iii) Given a12 = 37, d = 3, find a and S12.
(iv) Given a3 = 15, S10 = 125, find d and a10.
(v) Given d = 5, S9 = 75, find a and a9.
(vi) Given a = 2, d = 8, Sn = 90, find n and an.
(vii) Given a = 8, an = 62, Sn = 210, find n and d.
(viii) Given an = 4, d = 2, Sn = − 14, find n and a.
(ix) Given a = 3, n = 8, S = 192, find d.
(x) Given l = 28, S = 144 and there are total 9 terms. Find a.

Ans. (i) We are given a = 5, d = 3, an = 50

nth term of a AP is given by

an= a + (n -1)d

Where a = 5, d = 3 and an=50

50 = 5 + (n -1)3

(n -1)3 = 50 – 5 =45

n -1 = 15

n = 15 +1=16

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

= 16/2[2×5 + (16 – 1)3]

= 8(10 +15×3)

=8(10+45) = 8×55 =440

Sn= 440

Ans. (ii) We are given a = 7, a13 = 35

nth term of a AP is given by

an= a + (n -1)d

Where a = 7,  and a13=35⇒n =13

a13= a + (13 -1)d

35 = 7 + 12d

12d = 35 -7 =28

d = 28/12 =7/3

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

= 13/2[2×7 + (13 – 1)×7/3]

= 13/2(14 +12×7/3)

=13/2(14+28) = 13/2×42 =13×21 =273

Sn= 273

(iii)Given a12 = 37, d = 3,

nth term of a AP is given by

an= a + (n -1)d

Where  d = 3 and a12=37⇒n=12

37 = a + (12 -1)3

a+11×3 = 37

a+33= 37

a = 37 -33=4

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

⇒n/2(a +l) where l = a + (n -1)d

=12/2(4 +37)

=6×41 =246

### NCERT Solutions for Class 10 Maths Exercise 5.3 Chapter 5 Arithmetic Progression

(iv)Given a3 = 15, S10 = 125,

nth term of a AP is given by

an= a + (n -1)d

Where   and a3=15⇒n=3

15= a + (3 -1)d

a +2d = 15…..(i)

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

Where S10 = 125⇒n =10

S10= 10/2[2a + (10 – 1)d]

125 =5(2a +9d)

2a +9d =25……(ii)

Multiplying equation (i) by 2 and subtracting it from equation (ii)

5d =-5

d = -1

Putting d =-1 in equation (i)

a +2×-1 = 15

a -2 = 15

a = 15 +2 =17

a10= 17 + (10 -1)×-1 =17 +9×-1 =17 -9 =8

(v)Given d = 5, S9 = 75,

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

Where S9 = 75⇒n =9

S9= 9/2[2a + (9 – 1)5]

75 =9/2(2a +40)

2a +40 =150/9 =50/3

2a =50/3 -40 =(50 -120)/3=-70/3

a = -35/3

nth term of a AP is given by

an= a + (n -1)d

a9= -35/3 + (9 -1)5 =-35/3 +40 =(-35 +120)/3 =85/3

(vi)Given a = 2, d = 8, Sn = 90

nth term of a AP is given by

an= a + (n -1)d

Where a=2, d = 8

an= 2 + (n -1)8….(ii)

It is given that

Sn = 90

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

90=n/2(a +an) …….(ii) ,where an= a + (n -1)d

From equation (i)

90=n/2[2 +2 + (n -1)8]

n[2 +2 + (n -1)8] =180

4n +n(n -1)8 =180

8n² -8n +4n =180

8n² – 4n -180 =0

2n² – n – 45 =0

2n² – 10n+9n – 45 =0

2n(n – 5) + 9(n – 5) =0

(n – 5)(2n +9) =0

n =5,n = -9/2(canceling it since -9/2 is not a natural no.)

an= 2 + (n -1)8 =2 +(5 -1)8 =2 +4×8 = 2+32 =34

(vii) Given that a = 8, an = 62, Sn = 210

nth term of a AP is given by

an= a + (n -1)d

Where a=8, an = 62

62 = 8 + (n -1)d

(n -1)d = 54….(i)

The sum of n terms of an AP is given by

Sn= n/2[2a + (n – 1)d]

From equation (i)

210=n/2(2×8 +54)=n/2(16 +54)=n/2(70) =35n

35n = 210

n =210/35 =6

Putting the value n =6 in the equation (i)

(6 -1) d =54

5d =54

d = 54/5 =10.8

(viii) Given that  an = 4, d = 2, Sn = − 14

nth term of a AP is given by

an= a + (n -1)d

Where d=2, an = 4

4 = a + (n -1)2

2n+a  = 6….(i)

The sum of n terms of an AP is given by

Sn = n/2[2a + (n – 1)2]

Putting the value a =6-2n from the  equation (i)

− 14= n/2[2(6 -2n) + (n – 1)2]

-14 = n/2[12 -4n+ 2n – 2]

-14 = n/2(10 – 2n)

-28 = n(10 -2n)

10n – 2n² +28 = 0

2n² – 10n -28 =0

n² – 5n – 14 =0

n² – 7n +2n- 14 =0

n(n -7) + 2(n – 7) =0

(n -7)(n +2) =0

n =7, -2 (neglecting it since -2 is not a natural number)

Putting the value n =7 in the equation (i)

2×7+a  = 6

14 +a =6

a = 6 -14 = -8

(ix) Given that a = 3, n = 8, S = 192,

The sum of n terms of an AP is given by

Sn = n/2[2a + (n – 1)d]

192 = 8/2[2×3 +(8 -1)d]

4(6 +7d) = 192

6 +7d = 192/4 =48

7d = 48 – 6 =42

d = 42/7 =6

(x) Given that l = 28, S = 144 and there are total 9 terms

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

= n/2(a +l), where l = a + (n -1)d

144=9/2(a +28)

a +28 = (144 ×2)/9 =16×2 = 32

a = 32 – 28 = 4

Q4.How many terms of the AP. 9, 17, 25 … must be taken to give a sum of 636?

Ans.Let there are n terms of the AP. 9, 17, 25 …to give sum of 636

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

Where a =9, d = 17 – 9 =8 and Sn= 636

Sn= n/2[2×9 +(n -1)8]

636= n/2[18 +(n -1)8]

n/2[18 +(n -1)8] =636

9n + 4n² -4n -636 = 0

4n² + 5n – 636 = 0

4n² + 53n -48n- 636 = 0

n(4n +53) – 12(4n + 53) =0

(4n +53)(n -12) =0

n = -53/4, n = 12

Neglecting n = -53/4, since it is not a natural number

Hence there are the first 12 terms in the AP to give the sum of 636

Q5.The first term of an AP is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference.

Ans.The sum of n terms of the AP is given by

S= n/2[2a + (n – 1)d]

400=n/2(a +an)  ,where an= a + (n -1)d

Where a =5, an= 45 and S =400

400=n/2(5+45) =n/2(50) =25n

n = 400/25 =16

nth term of an AP is given by

an= a + (n -1)d

45 = 5 + (16 -1)d

(16 -1)d = 40

15d =40

d = 40/15 =8/3

Q6.The first and the last term of an AP are 17 and 350, respectively. If the common difference is 9, how many terms are there and what is their sum?

Ans.nth term of an AP is given by

an= a + (n -1)d

Where an= 350, a = 17,d =9

350= 17 + (n -1)9 = 17 +9n – 9

9n + 8 = 350

9n = 350 – 8 = 342

n = 342/9 = 38

The sum of n terms of the AP is given by

S= n/2[2a + (n – 1)d]

S=38/2(a +an)  ,where an= a + (n -1)d

Where a =17, an= 350

S=19(17 +350) =19×367 =6973

Q7. Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149.

Ans:nth term of an AP is given by

an= a + (n -1)d

Where a22= 149,d =7,n =22

149= a + (22 -1)7

149= a + 21×7 = a +147

a = 149 – 147 = 2

The sum of n terms of the AP is given by

S= n/2[2a + (n – 1)d]

S=n/2(a +an)  ,where an= a + (n -1)d

Putting the value n =22,a =2 and an=22

Sum of 22 terms is

S=22/2(2+149)=11×151 = 1661

Q8.Find the sum of first 51 terms of an AP whose second and third terms are 14 and 18, respectively.

Ans.nth term of an AP is given by

an= a + (n -1)d

Where a2= 14, a3= 18 =7

a2= a + (2 -1)d = a +d

a + d=14 …..(i)
18 =a + (3-1)d
a +2d =18……(ii)
Substracting equation (i) from the equation (ii)
d = 4
Putting the valu3 d =4 in the equation (i)
a +4 =14
a = 10
The sum of n terms of the AP is given by
S= n/2[2a + (n – 1)d]
The sum of 51 terms of the APS = 51/2[2×10 +(51 -1)4]S= 51/2[20 +50×4]= 51/2[20 +200]= 51/2×220 =51×110 =5610

Q9.If the sum of first 7 terms of an AP is 49 and that of 17 terms is 289, find the sum of first n terms.

Ans.The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

n = 7, S7= 49, , S17= 289

S7= 7/2[2a + (7- 1)d]

7/2[2a + 6d] = 49

a +3d = 7……(i)

S17= 17/2[2a + (17- 1)d]

17/2[2a +16d] = 289

a +8d = 17……..(ii)

Substracting equation (i) from equation (ii)

5d =10

d =10/5 =2

Putting the value of d in the equation (i)

a +3×2 =7

a = 1

The sum of n terms of the AP is given by

Sn= n/2[2×1 + (n – 1)2]

=n/2[2×1 + 2n – 2]

=n/2[2 -2 +2n]

=n/2[2n]

=n²

Q10.Show that a1, a2, ……. an,…… form an AP where an is defined as below:
(i) an = 3 + 4n
(ii) an = 9 – 5n
Also find the sum of the first 15 terms in each case

Ans.(i) nth term of  the given AP ,an is defined as

an = 3 + 4n

a1 = 3 + 4×1 =3 +4 =7

a2 = 3 + 4×2 = 3 + 8 =11

a3 = 3 + 4×3 = 3 +12 =15

…………. and so on

d = a2-a1 =11 -7 =4

a = a1 =7

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

The sum of the first 15 terms

S15=15/2[2×7 + (15-1)4]

=15/2[14 +14×4]

=15/2[14 +56]

S15=15/2(70) =15×35 =525

(ii) nth term of  the given AP ,an is defined as

an = 9 – 5n

a1 = 9 – 5×1 =9 -5 =4

a2 = 9 – 5×2 = 9 – 10 =-1

a3 = 9 – 5×3 = 9 -15 =-6

…………. and so on

d = a2-a1 =-1 -4 =-5

a = a1 =4

The sum of n terms of the AP is given by

Sn= n/2[2a + (n – 1)d]

The sum of the first 15 terms

S15=15/2[2×4 + (15-1)×-5]

=15/2[8 +14×-5]

=15/2[8 -70]

S15=15/2(-62) =15×-31 =-465

Q11.If the sum of the first n terms of an AP is 4n − n2, what is the first term (that is S1)? What is the sum of first two terms? What is the second term? Similarly find the 3rd, the10th and the nth terms.

Ans. The sum of the first n terms of an AP is 4n − n2

Sn=4n − n2

S1=4×1 − 12= 4 – 1=3, first term,a =3

S2=4×2 − 22= 8- 4=4,secod term = S2-S1=4 -3 =1

S3=4×3 − 32= 12- 9=3,third term = S3-S2=3 -4 =-1

S9=4×9 − 92= 36- 81=-45

S10=4×10 − 102= 40- 100=-60,10th  term = S10-S9=-60+45 =-15

nth term of an AP is given by

an= a + (n -1)d

Where first term,a =3,d =1-3 =-2

an= 3 + (n -1)×-2 =3 -2n +2 =5 -2n

The NCERT questions of the whole of the chapter 5 Arithmetic Progression are based on the two formulas

The nth term of the AP a ,a +d,a +2d ,……….an is given as

an= a + (n -1)d

Sum of n terms of the AP a ,a +d,a +2d ,……….an is given as

Sn=n/2 [2a + (n -1)d]

Where a =first term of the AP, d = common difference, an=nth term of the AP, and Sn is the sum of n terms of an AP

The sum of n terms of an AP can also be rewritten as

Sn=n/2 [a +l],where l = an,the last term of the AP

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