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Find the sum of 5+8+11+14+.........+89 |
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Answer» an=a+(n-1)d 89=5+(n-1)3 89=5+3n-3 89=2+3n n=29 Sn=n/2[2A+(n-1)d] =29/2[10+84] =29/2[94] =29×47 =1363 |
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