Arithmetic Sequences and Series

Question Types
All Questions
jee-main 2024 Q82 Arithmetic-Geometric Hybrid Problem
If $8 = 3 + \frac { 1 } { 4 } ( 3 + p ) + \frac { 1 } { 4 ^ { 2 } } ( 3 + 2 p ) + \frac { 1 } { 4 ^ { 3 } } ( 3 + 3 p ) + \ldots \infty$, then the value of $p$ is
jee-main 2024 Q82 Counting or Combinatorial Problems on APs
Let the positive integers be written in the form : If the $k ^ { \text {th} }$ row contains exactly $k$ numbers for every natural number $k$, then the row in which the number 5310 will be, is $\_\_\_\_$
jee-main 2024 Q82 Compute Partial Sum of an Arithmetic Sequence
An arithmetic progression is written in the following way
2
11514817
20232629

The sum of all the terms of the $10 ^ { \text {th} }$ row is $\_\_\_\_$
jee-main 2024 Q82 Telescoping or Non-Standard Summation Involving an AP
If $\left( \frac { 1 } { \alpha + 1 } + \frac { 1 } { \alpha + 2 } + \ldots \ldots + \frac { 1 } { \alpha + 1012 } \right) - \left( \frac { 1 } { 2 \cdot 1 } + \frac { 1 } { 4 \cdot 3 } + \frac { 1 } { 6 \cdot 5 } + \ldots . + \frac { 1 } { 2024 \cdot 2023 } \right) = \frac { 1 } { 2024 }$, then $\alpha$ is equal to $\_\_\_\_$
jee-main 2025 Q1 Compute Partial Sum of an Arithmetic Sequence
If the first term of an A.P. is 3 and the sum of its first four terms is equal to one-fifth of the sum of the next four terms, then the sum of the first 20 terms is equal to
(1) - 1080
(2) - 1020
(3) - 1200
(4) - 120
jee-main 2025 Q2 Find Specific Term from Given Conditions
Consider an A.P. of positive integers, whose sum of the first three terms is 54 and the sum of the first twenty terms lies between 1600 and 1800. Then its $11^{\text{th}}$ term is:
(1) 90
(2) 84
(3) 122
(4) 108
jee-main 2025 Q12 Compute Partial Sum of an Arithmetic Sequence
Let $S_n = \frac{1}{2} + \frac{1}{6} + \frac{1}{12} + \frac{1}{20} + \ldots$ upto $n$ terms. If the sum of the first six terms of an A.P. with first term $-p$ and common difference $p$ is $\sqrt{2026 S_{2025}}$, then the absolute difference between $20^{\text{th}}$ and $15^{\text{th}}$ terms of the A.P. is
(1) 20
(2) 90
(3) 45
(4) 25
jee-main 2025 Q13 Counting or Combinatorial Problems on APs
Suppose that the number of terms in an A.P. is $2k , k \in N$. If the sum of all odd terms of the A.P. is 40 , the sum of all even terms is 55 and the last term of the A.P. exceeds the first term by 27 , then k is equal to :
(1) 6
(2) 5
(3) 8
(4) 4
jee-main 2025 Q14 Compute Partial Sum of an Arithmetic Sequence
Let $\mathrm { T } _ { \mathrm { r } }$ be the $\mathrm { r } ^ { \text {th} }$ term of an A.P. If for some $\mathrm { m } , T _ { m } = \frac { 1 } { 25 } , T _ { 25 } = \frac { 1 } { 20 }$, and $20 \sum _ { \mathrm { r } = 1 } ^ { 25 } T _ { \mathrm { r } } = 13$, then $5 \mathrm { m } \sum _ { \mathrm { r } = \mathrm { m } } ^ { 2 \mathrm { m } } T _ { \mathrm { r } }$ is equal to
(1) 98
(2) 126
(3) 142
(4) 112
jee-main 2025 Q15 Compute Partial Sum of an Arithmetic Sequence
In an arithmetic progression, if $S_{40} = 1030$ and $S_{12} = 57$, then $S_{30} - S_{10}$ is equal to:
(1) 525
(2) 510
(3) 515
(4) 505
jee-main 2025 Q22 Find Specific Term from Given Conditions
The roots of the quadratic equation $3 x ^ { 2 } - \mathrm { p } x + \mathrm { q } = 0$ are $10 ^ { \text {th} }$ and $11 ^ { \text {th} }$ terms of an arithmetic progression with common difference $\frac { 3 } { 2 }$. If the sum of the first 11 terms of this arithmetic progression is 88, then $q - 2 p$ is equal to
jee-main 2025 Q22 Compute Partial Sum of an Arithmetic Sequence
Let $a _ { 1 } , a _ { 2 } , \ldots , a _ { 2024 }$ be an Arithmetic Progression such that $a _ { 1 } + \left( a _ { 5 } + a _ { 10 } + a _ { 15 } + \ldots + a _ { 2020 } \right) + a _ { 2024 } = 2233$. Then $a _ { 1 } + a _ { 2 } + a _ { 3 } + \ldots + a _ { 2024 }$ is equal to $\_\_\_\_$
jee-main 2025 Q24 Counting or Combinatorial Problems on APs
The interior angles of a polygon with $n$ sides, are in an A.P. with common difference $6 ^ { \circ }$. If the largest interior angle of the polygon is $219 ^ { \circ }$, then n is equal to
kyotsu-test 2012 QCourse2-II Summation of Derived Sequence from AP
Consider a sequence $\{a_n\}$ $(n = 1, 2, 3, \cdots)$ where the sum of the first $n$ terms is
$$\sum_{k=1}^{n} a_k = n^2 + 3n$$
(1) Then $a_n = \mathbf{A}\, n + \mathbf{B}$.
(2) For the sequence $\{b_n\}$ $(n = 1, 2, 3, \cdots)$, where $b_n = n^2 - 5n - 6$, the number of terms satisfying $b_n < 0$ is $\mathbf{C}$, and the sum of such terms is $-\mathbf{DE}$.
(3) It follows that for the sequences $\{a_n\}$ and $\{b_n\}$ in (1) and (2),
$$\sum_{k=1}^{n} \frac{k^2 b_k}{a_k} = \frac{1}{\mathbf{F}}\, n(n + \mathbf{G})\left(n^2 - \mathbf{H}\, n - \mathbf{I}\right).$$
kyotsu-test 2020 QCourse2-II-Q1 Optimization Involving an Arithmetic Sequence
Let $\{a_n\}$ be a sequence such that the sum $S_n$ of the terms from the first term to the $n$-th term is $$S_n = \frac{n^2 - 17n}{4},$$ and let $\{b_n\}$ be the sequence defined by $$b_n = a_n \cdot a_{n+5} \quad (n = 1, 2, 3, \cdots)$$
(1) For $\mathbf{A}$ $\sim$ $\mathbf{C}$ in the following sentences, choose the correct answer from among choices (0) $\sim$ (9) below.
Let us find the sum $T_n$ of the terms of sequence $\{b_n\}$ from the first term to the $n$-th term.
Since $a_n = \mathbf{A}$, we have $b_n = \mathbf{B}$. Hence we obtain $$T_n = \mathbf{C}.$$
(0) $\frac{n-7}{2}$
(1) $\frac{n-9}{2}$
(2) $\frac{n-11}{2}$
(3) $\frac{n^2 - 12n + 27}{4}$
(4) $\frac{n^2 - 13n + 36}{4}$
(5) $\frac{n^2 - 14n + 45}{4}$ (6) $\frac{n(n^2 - 17n + 83)}{12}$ (7) $\frac{n(n^2 - 17n + 89)}{12}$ (8) $\frac{n(n^2 - 18n + 83)}{12}$ (9) $\frac{n(n^2 - 18n + 89)}{12}$
(2) Next, let us find the minimum value of $T_n$.
When $n \leqq \mathbf{D}$ or $\mathbf{EF} \leqq n$, we see that $b_n > 0$. On the other hand, when $\mathbf{G} \leqq n \leqq \mathbf{H}$, we see that $b_n < 0$.
Hence $T_n$ is minimized at $n = \mathbf{I}$, $n = \mathbf{J}$ and $n = \mathbf{K}$, and its minimum value is $\mathbf{L}$. (Answer in the order such that $\mathbf{I} < \mathbf{J} < \mathbf{K}$.)
taiwan-gsat 2022 Q4 5 marks Properties of AP Terms under Transformation
Let the arithmetic sequence $\left\langle a _ { n } \right\rangle$ have first term $a _ { 1 }$ and common difference $d$ both positive, and $\log a _ { 1 } , \log a _ { 3 } , \log a _ { 6 }$ also form an arithmetic sequence in order. Select the common difference of the sequence $\log a _ { 1 } , \log a _ { 3 } , \log a _ { 6 }$.
(1) $\log d$
(2) $\log \frac { 2 } { 3 }$
(3) $\log \frac { 3 } { 2 }$
(4) $\log 2 d$
(5) $\log 3 d$
taiwan-gsat 2023 Q7 5 marks Compute Partial Sum of an Arithmetic Sequence
A company has two new employees, A and B, who start at the same time with the same starting salary. The company promises the following salary adjustment methods for employees A and B:
Employee A: After 3 months of work, starting the next month, monthly salary increases by 200 yuan; thereafter, salary is adjusted in the same manner every 3 months.
Employee B: After 12 months of work, starting the next month, monthly salary increases by 1000 yuan; thereafter, salary is adjusted in the same manner every 12 months.
Based on the above description, select the correct options.
(1) After 8 months of work, the monthly salary in the 9th month is 600 yuan more than in the 1st month
(2) After one year of work, in the 13th month, employee A's monthly salary is higher than employee B's
(3) After 18 months of work, in the 19th month, employee A's monthly salary is higher than employee B's
(4) After 18 months of work, the total salary received by employee A is less than the total salary received by employee B
(5) After two years of work, in the 12 months of the 3rd year, there are exactly 3 months where employee A's monthly salary is higher than employee B's
taiwan-gsat 2023 Q8 5 marks Counting or Combinatorial Problems on APs
An electronic billboard continuously alternates between playing advertisements A and B ($A$, $B$, $A$, $B \ldots$), with each advertisement playing for $T$ minutes (where $T$ is an integer). A person passes by just as advertisement A starts playing. 30 minutes later, the person returns to the location and sees advertisement B just starting to play. Select the options that could be the value of $T$.
(1) $15$ (2) $10$ (3) $8$ (4) $6$ (5) $5$
taiwan-gsat 2023 Q14 5 marks Counting or Combinatorial Problems on APs
From the 20 integers from 1 to 20, select three distinct numbers $a$, $b$, $c$ that form an arithmetic sequence with $a < b < c$. The number of ways to choose $(a, b, c)$ is $\square\square$.
taiwan-gsat 2025 Q12 5 marks Properties of AP Terms under Transformation
An arithmetic sequence has a first term of 1, a last term of 81, and 9 is also in the sequence. Let the number of terms in this sequence be $n$, where $n \leq 100$ . Select the correct options.
(1) $n$ is odd
(2) 41 must be in this arithmetic sequence
(3) The common difference of all arithmetic sequences satisfying the conditions is an integer
(4) There are 10 arithmetic sequences satisfying the conditions
(5) If $n$ is a multiple of 7, then $n = 21$
turkey-yks 2010 Q31 Sequence Defined by Recurrence with AP Connection
The sequences $\{a_{n}\}$ and $\{b_{n}\}$ are defined as follows. $$a_{n} = \begin{cases} 0, & \text{if } n \equiv 0 \pmod{3} \\ n, & \text{if } n \equiv 1 \pmod{3} \\ -n, & \text{if } n \equiv 2 \pmod{3} \end{cases}, \quad b_{n} = \sum_{k=0}^{n} a_{k}$$ Accordingly, what is $b_{4}$?
A) $-2$
B) $-1$
C) $0$
D) $2$
E) $3$
turkey-yks 2011 Q23 Compute Partial Sum of an Arithmetic Sequence
On day 1, Ismail puts one of each of the following coins into his piggy bank: 5 Kr, 10 Kr, 25 Kr, 50 Kr, and 1 TL. On day 2, he puts two of each, and continuing in this manner, on day n he puts n of each.
If Ismail has saved 104.5 TL in his piggy bank, what is n?
A) 10 B) 11 C) 12 D) 13 E) 14
turkey-yks 2012 Q9 Compute Partial Sum of an Arithmetic Sequence
The sum of all two-digit natural numbers with digit A in the units place is 504. What is A?
A) 5
B) 6
C) 7
D) 8
E) 9
turkey-yks 2013 Q9 Find Specific Term from Given Conditions
$$\frac { [ ( n + 1 ) ! ] ^ { 2 } + ( n ! ) ^ { 2 } } { [ ( n + 1 ) ! ] ^ { 2 } - ( n ! ) ^ { 2 } } = \frac { 61 } { 60 }$$
Given this, what is n?
A) 9
B) 10
C) 12
D) 13
E) 15
turkey-yks 2013 Q11 Counting or Combinatorial Problems on APs
For integers $\mathrm { x } , \mathrm { y }$ and z
$$2 x = 3 y = 5 z$$
Given this, which of the possible values of the sum $x + y + z$ is closest to 100?
A) 93
B) 96
C) 98
D) 103
E) 105