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Q1. A student observes that in the sequence 8000, 8500, 9000, 9500, ..., each term is obtained by adding 500 to the previous term. Which property of Arithmetic Progressions does this directly illustrate?
Answer: A — The definition of an AP requires that the difference between consecutive terms (common difference d) is constant; in this case d = 500, which is exactly what distinguishes an AP from other sequences.
Q2. Consider the ladder rung lengths: 45, 43, 41, 39, 37, 35, 33, 31. A student claims this is not an AP because the lengths are decreasing. Using the definition of an AP, is this claim correct?
Answer: B — An AP is defined by a constant common difference (here d = –2), not by whether the sequence increases or decreases; negative common differences are explicitly allowed by the AP definition.
Q3. Assertion (A): The sequence 3, 3, 3, 3, ... is an Arithmetic Progression. Reason (R): In this sequence, the common difference d = 0, and the definition of AP permits d to be zero. Choose the correct option:
Answer: A — Both statements are true; R directly explains why A is true because the definition explicitly states d can be any fixed number including zero.
Q4. A student is given the sequence –1.0, –1.5, –2.0, –2.5, ... and claims it cannot be an AP because it contains decimals and negative numbers. Based on the AP definition, evaluate this reasoning.
Answer: B — The AP definition makes no restriction on the type of numbers (integers, decimals, negative numbers are all allowed); here d = –0.5 is constant, confirming it is an AP.
Q5. Assertion (A): To completely determine an AP, you must know both the first term a and the common difference d. Reason (R): Knowing only a without d, or only d without a, does not allow you to write down the sequence uniquely. Choose the correct option:
Answer: A — R directly justifies A: without both parameters, different APs are possible (e.g., a = 6, d = 3 gives 6, 9, 12, ... while a = 6, d = –3 gives 6, 3, 0, ..., both different despite sharing one parameter).
Q6. A teacher writes two sequences on the board: Sequence P: 100, 150, 200, 250, ... and Sequence Q: 12, 22, 32, .... The teacher claims both are APs. Based on the AP definition, which claim is correct?
Answer: B — Sequence P has a constant common difference d = 50, making it an AP; Sequence Q (1, 4, 9, 16, ...) has differences 3, 5, 7, ... which are not constant, so it is not an AP.
Q7. For the general form of an AP: a, a + d, a + 2d, a + 3d, ..., a student writes the nth term as a + (n – 1)d instead of a + nd. Is this correct or incorrect?
Answer: B — The nth term formula a + (n – 1)d is correct because the first term (n = 1) is a + (1 – 1)d = a, the second term (n = 2) is a + (2 – 1)d = a + d, confirming the pattern.
Q8. Assertion (A): The list of heights 147, 148, 149, ..., 157 is a finite Arithmetic Progression. Reason (R): A finite AP has a last term, whereas infinite APs do not have a last term. Choose the correct option:
Answer: A — R directly explains A: the sequence has a clear last term (157) and constant difference (1), making it a finite AP by definition.
Q9. A student claims that the sequence 6, 9, 12, 15, ... proves that knowing only the common difference d = 3 is enough to determine an AP uniquely. Why is this claim incomplete?
Answer: B — Knowing d = 3 alone leaves infinitely many possible APs (3, 6, 9, ..., or 10, 13, 16, ..., etc.); both a and d are needed to uniquely determine the AP.
Q10. Assertion (A): The balance money sequence 950, 900, 850, 800, ..., 50 is an Arithmetic Progression. Reason (R): The common difference is –50, and each term is obtained by subtracting 50 from the previous term. Choose the correct option:
Answer: A — R directly justifies A: the constant difference d = –50 between consecutive terms is the defining property of an AP.
What is an Arithmetic Progression (AP)?
A sequence where each term is obtained by adding a fixed number (common difference d) to the preceding term.
What is the common difference d in an AP?
The fixed number added to each term to get the next term, found by subtracting any term from the term immediately following it.
Write the general form of an AP.
a, a+d, a+2d, a+3d, ... where a is the first term and d is the common difference.
Formula for the nth term of an AP
an = a + (n-1)d, where a is the first term, d is common difference, and n is the position of the term.
How do you identify if a list of numbers is an AP?
Check if the difference between any two consecutive terms is the same; if yes, it's an AP.
Can the common difference d be negative?
Yes, a negative d means the AP is decreasing (each term is smaller than the previous term).
What is a finite AP?
An AP that has a fixed number of terms and a last term (e.g., 45, 43, 41, ..., 31).
What is an infinite AP?
An AP that continues indefinitely without a last term (e.g., 1, 2, 3, 4, ...).
If a = 8 and d = 0, what kind of AP is formed?
A constant AP where all terms are the same: 8, 8, 8, 8, ... (common difference is zero).
What two pieces of information uniquely determine an AP?
The first term a and the common difference d; knowing both allows you to write any term or the entire sequence.
Write the first four terms of the AP where the first term a = 3 and the common difference d = -0.5. Is this AP finite or infinite? [2 marks]
Use the general form a, a+d, a+2d, a+3d to find the four terms. Then explain whether the AP stops at a specific term (finite) or continues forever (infinite) based on whether a last term is mentioned.
Reena's monthly salary starts at ₹8000 with an annual increment of ₹500. (a) How much will her salary be in the 5th year? (b) Write the AP representing her salary for the first 5 years. [3 marks]
Here a = 8000 and d = 500 (annual increment). Use the formula an = a + (n-1)d to find the 5th year salary. For part (b), list the terms: a, a+d, a+2d, a+3d, a+4d to show the AP for 5 years.
The ladder in Example (ii) has rungs whose lengths decrease uniformly by 2 cm from bottom to top, with the bottom rung being 45 cm. (a) Find the length of the 8th rung from the bottom. (b) Find the sum of the lengths of all 8 rungs. (c) Is this AP finite or infinite, and why? [5 marks]
Identify a = 45 (bottom rung), d = -2 (decrease), and n = 8. Use an = a + (n-1)d to find the 8th rung. For the sum, use Sn = n/2[2a + (n-1)d] or Sn = n/2(first + last). For part (c), explain that since the ladder has exactly 8 rungs, the AP has a fixed last term, making it finite.
Q1. Assertion (A):
The sequence 5, 10, 15, 20, ... is an Arithmetic Progression.
Reason (R):
The difference between any two consecutive terms is constant and equal to 5.
Answer: A — Both A and R are true, and R is the correct explanation of A — Both the assertion and reason are true, and the reason directly explains why the sequence is an AP. A constant common difference (d = 5) is the defining characteristic of an AP, making the reason the correct explanation for the assertion.
Q2. Assertion (A):
In the AP 20, 15, 10, 5, 0, ..., the common difference is -5.
Reason (R):
The sequence is decreasing, so the common difference must be negative.
Answer: B — Both A and R are true, but R is NOT the correct explanation of A — Both assertion and reason are true. The common difference is indeed d = 15 - 20 = -5. However, the reason (sequence is decreasing, therefore d is negative) is not the complete logical explanation. The common difference is -5 because we calculate a₂ - a₁ = 15 - 20 = -5, regardless of whether it's decreasing. The reason describes an observation rather than the defining principle.
Q3. Assertion (A):
The sequence 2, 4, 8, 16, ... is an Arithmetic Progression.
Reason (R):
Each term is obtained by adding a fixed number to the previous term.
Answer: D — A is false but R is true — The assertion is false because 2, 4, 8, 16, ... is a geometric progression where each term is multiplied by 2, not an AP. The reason is also false in this context because the sequence does not have a constant additive difference. The differences are 2, 4, 8, which are not constant.
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Case Study:
Reena got a job with a starting monthly salary of ₹8000. According to her contract, she receives an annual increment of ₹500. Her salary for the 1st year is ₹8000, 2nd year is ₹8500, 3rd year is ₹9000, and so on. Reena wants to calculate her salary progression over several years to plan her finances.
Q1. What is the common difference in Reena's salary progression?
Answer: A
Q2. What will be Reena's salary in the 6th year?
Answer: B
Q3. In which year will Reena's salary reach ₹12000?
Answer: B
Q4. Identify the correct AP representation of Reena's salary scheme.
Answer: A
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Real CBSE board exam questions from past papers — free to attempt.
CBSE 2026 · Set 31/4/1 · 1 mark
The sum of first n terms of an A.P. is 502. If the first and the last terms are 2 and 192 respectively, then the value of n is:
CBSE 2026 · Set 31/4/1 · 1 mark
nth term of the A.P. –3/2, 3/2, 9/2, ... is:
CBSE 2026 · Set 31/4/1 · 5 marks
The third and ninth term of an A.P. are 4 and – 8 respectively. (i) Which term of the A.P. is zero? (ii) Find the value of n if Sₙ = – 36.
CBSE 2026 · Set 31/4/2 · 1 mark
nth term of an A.P. is 5n – 15. The common difference of the A.P. is:
CBSE 2026 · Set 31/4/2 · 1 mark
nth term of the A.P. – 3/2, 3/2, 9/2, ... is:
CBSE 2026 · Set 31/4/3 · 5 marks
The third and ninth term of an A.P. are 4 and –8 respectively. (i) Which term of the A.P. is zero? (ii) Find the value of n if Sn = –36.
CBSE 2026 · Set 31/5/1 · 1 mark
nth term of the A.P.: 4/3, –1/3, 3, ... is
CBSE 2026 · Set 31/5/1 · 1 mark
If –26, x, 2 are in A.P., then the value of x is
CBSE 2026 · Set 31/5/1 · 3 marks
In an A.P., it is given that a = 2, d = 8 and Sn = 90. Find the value of n.
CBSE 2026 · Set 31/5/2 · 1 mark
If 16/9, –2/9, –20/9, .... are in A.P., then next term of the sequence is
CBSE 2026 · Set 31/5/2 · 3 marks
(a) How many terms of the A.P. 3, 5, 7, 9, ... must be added to get the sum 80? OR (b) Find three consecutive terms in A.P. whose sum is 21 and their product is 231.
CBSE 2026 · Set 31/5/3 · 1 mark
If 14th term of an A.P. is 4 and its 15th term is zero, then its first term is
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