Search for: Sum of the first 20 terms of the series 1(2)(4)+(1)(3)(2)(4)(6)+(1)(3)(5)(2)(4)(6)(8)+… is Sum of the first 20 terms of the series 1(2)(4)+(1)(3)(2)(4)(6)+(1)(3)(5)(2)(4)(6)(8)+… is A12−1240 40C20B12−1241 42C21C12−1242 42C21D12−1243 40C20 Fill Out the Form for Expert Academic Guidance!l Grade ---Class 1Class 2Class 3Class 4Class 5Class 6Class 7Class 8Class 9Class 10Class 11Class 12 Target Exam JEENEETCBSE +91 Preferred time slot for the call ---9 am10 am11 am12 pm1 pm2 pm3 pm4 pm5 pm6 pm7 pm8pm9 pm10pm Please indicate your interest Live ClassesBooksTest SeriesSelf Learning Language ---EnglishHindiMarathiTamilTeluguMalayalam Are you a Sri Chaitanya student? NoYes Verify OTP Code (required) I agree to the terms and conditions and privacy policy. Solution:Let ak denote the kth term of the series, thenak=(1)(3)(5)⋯(2k−1)(2)(4)(6)⋯(2k)(2k+2)=(1)(3)(5)⋯(2k−1)(2k+2−2k−1)(2)(4)(6)⋯(2k)(2k+2)=bk−bk+1wherebk=(1)(3)(5)⋯(2k−1)(2)(4)(6)⋯(2k)=(1)(2)(3)(4)⋯(2k−1)(2k)[(2)(4)(6)⋯(2k)]2=122k 2kCkThus,∑k=120 ak=∑k=120 bk−bk+1=b1−b21=12−1242 42C21 Related content Nucleus Diagram for Class 9 Neuron Diagram Class 9 Human Heart Diagram Class 10 CBSE Class 7 Science Chapter 1 Nutrition in Plants MCQ Questions with Answers CBSE Class 9 English Worksheet – The Road not Taken 50+ GK Questions and Answers for Class 8 “Kabir Ki Sakhiyan” MCQ Questions for Class 9 Hindi with Answers Kshitij, Kritika, Sparsh, Sanchayan Bhag 1 CBSE Class 7 English Honeycomb Chapter 1 Three Questions MCQ Questions with Answers CBSE Class 9 English Beehive Book Poem 1 The Road Not Taken MCQ Questions with Answers MCQs Questions with Answers for Class 9 English Chapter 1 The Fun They Had