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Question 36 [Case Based] Ms. Sheela visited a store near her house and found that the glass jars are arranged one above the other in a specific pattern. On the top layer there are 3 jars. In the next layer there are 6 jars. In the 3rd layer from the top there are 9 jars and so on till the 8th layer. The jars look like Question 36 (iii) (A) (iii) (A) If there are ‘n’ number of rows in a layer then find the expression for finding the total number of jars in terms of n. Hence find 𝑆_8 .Now, AP is 3, 6, 9, …. upto 8 terms We need to find Sn in terms of n. Now, Sn = 𝑛/2 [2a + [n − 1]d] Putting a = 3, d = 3 = 𝑛/2 [2(3) + [n − 1]3] = 𝑛/2 [6 + 3n − 3] = 𝒏/𝟐 [3 + 3n] Thus, Sn = 𝑛/2 [3 + 3n] We also need to find s8 Putting n = 8 in Sn S8 = 𝟖/𝟐 [3 + 3 × 8] = 4 [3 + 24] = 4 × 27 = 108

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo