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Chapter 6: Arithmetic Progressions > Hard Level Worksheet

Hard Level Worksheet

Very Short Answer Questions (1 Mark Each)

(1) Write the 20th term of the A.P. whose first term is 3 and common difference is 7. a20 =

Perfect! Using the formula an = a + (n-1)d for the nth term.

(2) If Sn = n(2n + 1), find the first term of the A.P. First term a1 =

Correct! The first term is always S1 when given the sum formula.

(3) What is the common difference of the A.P. whose a3 = 8 and a13 = 44? d = (Enter in fraction form)

Excellent! Used the relationship between any two terms to find d.

(4) The 3rd and 7th terms of an A.P. are 10 and 26 respectively. Find the 1st term. a1 =

Perfect systematic approach to finding the first term!

Short Answer Questions (2 Marks Each)

Note: Answer each question with steps and explanation, in 2-3 sentences. Write down the answers on sheet and submit to the school subject teacher.

(1) Find the number of terms in the A.P. 7, 13, 19, ...., 301.

First term a = , Common difference d = with n =

Excellent! The A.P. has 50 terms.

(2) The sum of the first n terms of an A.P. is 5n2 + 3n. Find the 7th term. a7 =

Perfect! Used the relationship an = Sn - Sn1 for n > 1.

(3) The sum of the first 12 terms of an A.P. is 420. If the first term is 10, find the common difference. d = (Enter in fraction form)

Excellent application of the sum formula!

(4) If 5 times the 5th term of an A.P. is equal to 3 times the 9th term, find the ratio of the 1st term to the common difference. a:d =

Perfect algebraic manipulation to find the ratio!

Long Answer Questions (4 Marks Each)

Note: Answer each question with steps and explanation. Write down the answers on sheet and submit to the school subject teacher.

(1) The sum of first n terms of an A.P. is given by Sn = 2n2 + 3n. Find its 10th term. Also, find the A.P.

10th term: a10 = with the AP being , , , , ...

(2) A sum of ₹ 1000 is divided among three children in such a way that their shares are in A.P. and the product of the first and third share is 15,625. Find their individual shares. The shares are: ₹,, (Enter upto two decimal places)

Excellent problem involving A.P. with constraints!

(3) In an A.P., the sum of the first p terms is equal to the sum of the next q terms. Show that (2p + q - 1)d = -2a, where a is the first term and d is the common difference.

Part B: Objective Questions (1 Mark Each)

Choose the correct answer and write the option (a/b/c/d)

(1) The nth term of the A.P. 3, 6, 9, … is:

(a) 3n (b) 3n + 1 (c) 2n + 1 (d) 2n

3n
3n + 1
2n + 1
2n

Correct! First term a = 3, common difference d = 3, so an = 3 + (n-1)×3 = 3n.

(2) If the sum of n terms of an A.P. is 4n + n2, the first term is:

(a) 5 (b) 4 (c) 1 (d) Cannot be determined

5
4
1
Cannot be determined

Correct! First term a1 = S1 = 4(1) + 12 = 5.

(3) Which of the following A.Ps has a negative common difference?

(a) 8, 6, 4, 2 (b) 10, 20, 30 (c) 0, 0, 0 (d) 5, 7, 9

8, 6, 4, 2
10, 20, 30
0, 0, 0
5, 7, 9

Correct! Common difference = 6 - 8 = -2 < 0.

(4) In an A.P., a = 4, d = -2, then a10 =

(a) -14 (b) -16 (c) -18 (d) -12

-14
-16
-18
-12

Correct! a10 = 4 + (10-1)×(-2) = 4 - 18 = -14.

(5) The sum of the first 20 terms of the A.P. 1, 3, 5, … is

(a) 400 (b) 200 (c) 420 (d) 380

400
200
420
380

Correct! S20 = 2022×1+201×2 = 102+38 = 400.

(6) Which term of the A.P. 25, 22, 19, … is zero?

(a) 9th (b) 10th (c) 11th (d) 12th

9th
10th
11th
12th

Correct! Setting an = 0: 25 + (n-1)×(-3) = 0, so n = 9.

(7) If Sn = 2n2 + 3n, then a4 =

(a) 29 (b) 30 (c) 31 (d) 17

29
30
31
17

Correct!

(8) In an A.P., a = -2, d = 5, find the sum of the first 15 terms.

(a) 505 (b) 520 (c) 540 (d) 555

495
520
540
555

Correct! S15 = 1522×2+151×5 = 1524+70 = 152×66 = 495.

(9) In how many terms of the A.P. 5, 8, 11, … is the sum 450?

(a) 10 (b) 12 (c) 15 (d) 18

10
12
15
18

Correct! Using Sn = n22×5+n1×3 = 450, solving gives n = 12.

(10) If the 3rd term of an A.P. is 8 and the 7th term is 20, what is the sum of the first 10 terms?

(a) 120 (b) 130 (c) 140 (d) 150

120
155
140
150

Correct! From given terms: d = 3, a = 2. Then S10 = 1022×2+9×3 = 5×31 = 155.

In an A.P., if aₙ = a + (n-1)d, then a₁₀ − a₆ = 4d.
If Sₙ = n/2 [2a + (n-1)d], then Sₙ₊₁ − Sₙ = aₙ₊₁.
In an A.P., if a₃ = 10 and a₇ = 22, then d = 4.
If the sum of the first n terms of an A.P. is quadratic in n, then the sequence is an arithmetic progression.
The difference between consecutive sums Sₙ of an A.P. is always equal to the common difference d.
If the 5th term of an A.P. is twice its 2nd term, then d = a/3.
True
False

Arithmetic Progressions Challenge

Determine whether these statements about A.P.s are True or False:

In A.P., aₙ = a + (n-1)d
aₙ = Sₙ - Sₙ₋₁ for n > 1
All A.P.s have positive common difference
If d = 0, the sequence is not an A.P.
Every A.P. has a finite number of terms
Sum formula: Sₙ = n/2[first term + last term]

Arithmetic Progressions Quiz

🎉 You Did It! What You've Learned:

By completing this worksheet, you now have a solid understanding of:

(1) A.P. Formula Mastery: Using an = a + (n-1)d for finding any term

(2) Sum Calculations: Applying Sn = n22a+n1d and Sn = n2first+last

(3) Term Relations: Finding unknown terms using given conditions

(4) Real-world Applications: Money distribution and practical A.P. problems

(5) Algebraic Manipulation: Proving relationships and deriving formulas

(6) Problem-solving Strategies: Working with constraints and multiple conditions

(7) Sequence Analysis: Identifying patterns and properties of arithmetic sequences

(8) Advanced Techniques: Using sum formulas to find individual terms

Excellent work mastering arithmetic progressions and their diverse applications!