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Find the sum of 20 odd natural number |
| Answer» First 20 odd natural numbers are :-1,3,5,7,...... upto 20 termsSo, it is an Arithmetic sequence with a =1,d =2We know that,sum of n terms of an A.P. is given by:-Sn\xa0=\xa0{tex}\\frac {n} {2}{/tex}\xa0[ 2a + (n - 1)d ]\xa0=\xa0{tex}\\frac {20} {2}{/tex}\xa0[ 2×1 + (20 -1)×2 ]\xa0= 10 [2 + 38] = 40×10 = 400 | |