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Example 5 - Determine AP whose 3rd term is 5 and 7th term

Example 5 - Chapter 5 Class 10 Arithmetic Progressions - Part 2
Example 5 - Chapter 5 Class 10 Arithmetic Progressions - Part 3

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Example 5 Determine the AP whose 3rd term is 5 and the 7th term is 9. We know that an = a + (n – 1)d From (1) & (2) 5 – 2d = 9 – 6d 6d – 2d = 9 – 5 Given 3rd term is 5 a3 = a + (3 – 1)d 5 = a + 2d a = 5 – 2d Given 7th term is 9 a7 = a + (7 – 1)d 9 = a + 6d a = 9 – 6d 4d = 4 d = 4/4 d = 1 Putting d = 1 in (1) a = 5 – 2d a = 5 – 2(1) a = 5 – 2 a = 3 Hence , First term of an A.P = 3 Second term of AP = First term + Common Difference = 3 + 1 = 4 Third term of AP = Second term + Common Difference = 4 + 1 = 5 So the A.P is 3, 4, 5, …………

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.