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Arithmetic Progression (AP) is a numerical series in which the difference between any two subsequent integers is a fixed value. Arithmetic Sequence is another name for Arithmetic Progression. For instance, the natural number sequence 1, 2, 3, 4, 5, 6, is an Arithmetic Progression with a common difference of 1 between two subsequent terms (say 1 and 2). (2 -1). Even when dealing with odd and even numbers, the common difference between two consecutive words will be equal to 2.
Ques: Find the sum of the first 5 terms of the AP: 10, 6, 2…
- –320
- 512
- 10
- –960
The video below explains this:
Arithmetic Progression Detailed Video Explanation:
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Ans: (c) 10
Explanation: AP: 10, 6, 2, …
a = 10, d = - 4
Sum of first n terms = S(n) = (n/2) x [2a + (n – 1) x d]
S5 = (5/2) x [2 x (10) + (5 – 1) x (-4)]
= (5/2) x [20 + 4 x (-4)]
= (5/2) x (20 – 16)
= (5/2) x (4)
= 5 x 2
= 10
Ques: The d for the series of numbers -12, –6, 0, 6… is
- –2
- 6
- 8
- -1
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Ans: (b) 6
Explanation:
–12, –6, 0, 6,…
Let a(1) = -12, a(2) = -6, a(3) = 0, a(4) = 6
First relational d,
a(2) – a(1) = -6 – (-12) = 6
Second relational d,
a(3) – a(2) = 0 – (-6) = 6
Third relational d,
a(4) – a(3) = 6 – (0) = 6
all the d are equals to each other, hence
d = 6.
Ques: Find the number of multiples of 4 falling between 10 and 250 is:
- 30
- 15
- 60
- 20
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Ans: (c) 60
Explanation: 4’s multiples are:
12, 16, 20, 24, …
a = 12 and d = 4
2 is the remainder for 250 / 4.
250 – 2 = 248 which is divisible by 2.
12, 16…248
nth term, a(n) = 248
a(n) = a + (n − 1) x d
- 248 = 12 + (n-1) × 4
236 / 4 = n - 1
59 = n - 1
n = 60
Ques. In the A.P. -3, -1/2, 2 …. The 11th term is
- 42
- -12
- 22
- 65
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Ans: (c) 22
Explanation: The A.P. is -3, -1/2, 2 …
Where a = – 3
d = a(2) – a(1) = (-1 / 2) - (-3)
⇒ (-1 / 2) + 3 = 5 / 2
a(n) = a + (n−1) x d
a(11) = 3 + (11-1) x (5 / 2)
a(11) = 3 + (10) x (5 / 2)
a(11) = -3 + 25
a(11) = 22
Ques: The name of the famous mathematician who is credited with discovering the total value of the very first 100 natural numbers is
- Gauss
- Pythagoras
- Euclid
- Newton
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Ans: (a) Gauss
Explanation: Gauss is the great mathematician who is credited with discovering the total value of the first 100 natural numbers.
Ques: For a given AP, a(n) = 4, n = 7, d = -4, find the value of a
- 51
- 37
- 2
- 28
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Ans: (d) 28
Explanation: d = -4, n = 7, a(n) = 4
a(n) = a + (n – 1) x d
a + (7 – 1) x (-4) = 4
a + 6 x (-4) = 4
a – 24 = 4
a = 4 + 24
a = 28
Ques: If a(17) exceeds it’s a(10) by 7. The d is:
- 2
- 4
- 1
- 3
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Ans: (c) 1
Explanation: for a given AP, the Nth term is:
a(n) = a + (n-1) x d
a(17) = a + (17−1) x d
a(17) = a + 16 x d
a(10) = a+9(d)
a(17) – a(10) = 7
(a + 16 x d) − (a + 9 x d) = 7
7 x d = 7
d = 1
Ques: 10, 7, 4, …, is an AP, what will be the 30th term of this series?
- 65
- 22
- -77
- 45
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Ans: (c) -77
Explanation: A.P. given in the question is 10, 7, 4, …
a = 10
d = a(2) – a(1) = 7 − 10 = −3
a(n) = a + (n−1) x d
a(30) = 10 + (30−1) x (−3)
a(30) = 10 + (29) x (−3)
a(30) = 10 − 87 = −77
Ques: What is the d of an AP in which a(18) – a(14) = 32?
- -6
- 1
- 5
- 8
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Ans: (d) 8
Explanation:
a(18) – a(14) = 32
a(n) = a + (n – 1) x d
a + (17) x d – (a + 13 x d) = 32
(17) x d – (13) x d = 32
(4) x d = 32
d = 8
Ques: 5, 8, 11, 14, … is an AP, what will be the a(10)?
- 23
- 12
- 32
- 95
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Ans: (c) 32
Explanation:
The given series : 5, 8, 11, 14, …
a = 5
d = 8 – 5 = 3
a(n) = a + (n – 1) x d
10th term = a(10) = a + (10 – 1) x d
= 5 + 9 x (3)
= 5 + 27
= 32
Ques: a and a(2) are -3 and 4, find the a(21) of the series.
- 26
- 95
- 137
- -43
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Ans: (c) 137
Explanation: a = -3 and a(2) = 4
a = -3
d = 4 - a = 4 - (-3) = 7
a(21)=a + (21-1) x d
= -3 + (20) x 7
= -3 + 140
= 137
Ques: For this given AP 3, 1, -1, -3, find the values of a and d is:
- 3, -2
- 0, 3
- 1, 2
- -2, 3
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Ans: (a) 3 and -2
Explanation: a = 3
d = a(2) – a(1)
⇒ 1 – 3 = -2
⇒ d = -2
Ques: Does 210 falls in the AP: 21, 42, 63, 84…? If yes, then on which term?
- 12th
- 10th
- 5th
- 7th
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Ans: (b) 10th
Explanation:
AP: 21, 42, 63, 84, …
a = 21
d = 42 – 21 = 21
a(n) = 210
a + (n – 1) x d = 210
21 + (n – 1) x (21) = 210
21 + 21 x n – 21 = 210
21 x n = 210
n = 10
Ques: The total value of the starting four multiples of 2 is:
- 20
- 65
- 45
- 30
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Ans: (a) 20
Explanation: The starting four multiples of 2 is 2, 4, 6, 8
a=2 and d=2
n=4
S(n) = (n / 2) x [2a + (n - 1) x d]
S(4) = (4 / 2) x [2 x (2) + (4 - 1) x 2]
= (2) x [4 + 6]
= (2) x [10]
= 20
Ques: On which number of term does 78 falls in the A.P. 3, 8, 13, 18, … is 78?
- 9th
- 20th
- 16th
- 4th
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Ans: (c) 16th
Explanation: Given, 3, 8, 13, 18, … is the AP.
a = 3
d = a(2) – a(1) = 8 − 3 = 5
Let a(n) term be 78.
a(n) = a + (n − 1) x d
78 = 3 + (n − 1) x 5
75 = (n − 1) x 5
(n − 1) = 15
n = 16
Ques: The first four terms of an AP whose a is 10 and d is 10 will be?
- 12, 24, 36, 48
- 8, 16, 24, 32
- 15, 30, 45, 60
- 10, 20, 30, 40
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Ans: (d) 10, 20, 30, 40
Explanation: a = 10, d = 10
a(1) = a = 10
a(2) = a1 + d = 10 + 10 = 20
a(3) = a2 + d = 20 + 10 = 30
a(4) = a3 + d = 30 + 10 = 40
Ques: In an AP, if d = -4, a = 28, n = 7, then an is:
- 2
- 1
- 4
- 5
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Ans: (c) 4
Explanation:
a(n) = a + (n - 1) x d
= 28 + (7 - 1) x (-4)
= 28 + 6 x (-4)
= 28 - 24
a(n) = 4
Ques: The missing terms in AP: __, 13, __, 3 are:
- 25, 5
- 15, 9
- 19, 7
- 18, 8
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Ans: (d)
Explanation: a2 = 13 and
a(4) = 3
The nth term of an AP;
a(n) = a + (n − 1) x d
a(2) = a + (2 - 1) x d
13 = a + d ………………. (i)
a(4) = a + (4 - 1) x d
3 = a + 3d ………….. (ii)
Subtracting equation (i) from (ii), we get
– 10 = 2 x d
d = – 5
put value of d in eq 1
13 = a + (-5)
a = 18
a(3) = 18 + (3 - 1) x (-5)
= 18 + 2 x (-5)
= 18 - 10 = 8
Ques: Starting from the last, the 20th term of the A.P. 3, 8, 13, …, 253 is:
- 131
- 123
- 137
- 158
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Ans: (d) 158
Explanation: A.P. is 3, 8, 13, …, 253
d= 5.
Starting from the end of the series,
253, 248, 243, …, 13, 8, 5
a = 253
d = 248 − 253 = −5
n = 20
a(20) = a + (20 − 1) x d
a(20) = 253 + (19) x (−5)
a(20) = 253 − 95
a(20) = 158
Ques: If the a(2) is 13 and a(5) is 25, then it’s a(7) is
- 23
- 65
- 15
- 33
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Ans: (d) 33
Explanation:
a(2) = 13
a + d = 13
a = 13 – d…. (i)
a(5) = 25
a + 4d = 25….(ii)
Substituting the value of (i) in (ii),
13 – d + 4 x d = 25
3 x d = 12
d = 4
So, a = 13 – 4 = 9
a(7) = a + 6d = 9 + 6(4) = 9 + 24 = 33
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