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Linear polynomials · 2 marks

A chess club charges a joining fee of ₹200 plus ₹50 for every match played. The following table shows the amount a player will have to pay as the number of matches varies.

Answer: For m matches the total cost is ₹(200 + 50m), a linear polynomial in m. The amount rises by a constant ₹50 per extra match.

Step-by-step solution

Given: Joining fee ₹200 (paid once); ₹50 for every match played
To find: The amount paid for 1, 2, 3, … and m matches

Idea: The joining fee is fixed; only the match charge grows. For m matches the match charge is 50 × m.

  1. Amount = 200 + 50 × (number of matches):
    Number of matches played12345…m
    Amount paid (₹)250300350400450…200 + 50m
    1 mark
  2. So for m matches the total cost is ₹(200 + 50m). The highest power of m is 1, so 200 + 50m is a linear polynomial in m.½ mark
  3. Each extra match adds the same ₹50 (250, 300, 350, …). This constant increase is what makes the pattern linear.½ mark
The total cost for m matches is ₹(200 + 50m), a linear polynomial in m; it increases by ₹50 for every additional match.

Check: For 4 matches: 200 + 50 × 4 = 400, which matches the table ✓.

Answer to write in the exam

Amount = 200 + 50 × (number of matches)

1, 2, 3, 4, 5 matches → ₹250, ₹300, ₹350, ₹400, ₹450

Amount increases by ₹50 for every additional match

∴ For m matches, amount = ₹(200 + 50m), a linear polynomial in m

Common mistakes that cost marks

  • Writing 250m (charging the joining fee for every match). The ₹200 is paid only once.
  • Writing 200m + 50. Here the fixed amount and the per-match amount have been swapped.
  • Forgetting the joining fee and writing 50m.

How this can come in the exam

MCQ (1 mark)

A gym charges ₹500 to join and ₹120 per session. The cost of s sessions is

  1. ₹620s
  2. ₹(500s + 120)
  3. ₹(500 + 120s)
  4. ₹(500 + 120)s
Show answer

(C) ₹(500 + 120s)
Fixed ₹500 plus 120 for each of the s sessions: 500 + 120s.

Case-based (4 marks)

A swimming club charges a registration fee of ₹300 and ₹40 per swim.
(i) Make a table of the amount paid for 1 to 4 swims. (ii) Write the amount for n swims. (iii) Is it a linear polynomial? Why? (iv) By how much does the amount increase for each extra swim?

Show answer(i) 340, 380, 420, 460 (1 mark). (ii) ₹(300 + 40n) (1 mark). (iii) Yes: the highest power of n is 1 (1 mark). (iv) ₹40, the constant difference (1 mark).

Try one yourself

A taxi app charges ₹60 booking fee and ₹18 per km. Write the fare for k km and find it for 12 km.

Show answer

₹(60 + 18k). For 12 km: 60 + 216 = ₹276.

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