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Difficulty: 3/102024 NMTC 2024 (QII-39)

The 6th and 17th terms of an A.P. are 19 and 41 respectively. Find the 40th term

Guide / Hint

Hint 1: Use the -th term formula of an AP: .

Hint 2: Write two linear equations: and . Subtract them to solve for , then solve for .

Hint 3: Apply the solved values of and to calculate .

Solution

Step 1 (Set up Equations): In an Arithmetic Progression (A.P.), the -th term is given by the formula , where is the first term and is the common difference.

  • The 6th term is 19:

  • The 17th term is 41:

Step 2 (Solve for d and a): Subtract Equation 1 from Equation 2:

Substitute back into Equation 1:

Step 3 (Find the 40th term): Using the values and , we compute :

Step 4 (Conclusion): The 40th term of the A.P. is exactly 87.

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    2024 NMTC 2024 QII-39 - Olympiad Math Olympiad Question | Leminno