Question

find the sum of 23rd term of the A.P.5,8,11,14…..............

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Answer 1

$\huge\bf{QUESTION}$

Find sum of 23 terms of Ap!

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$\huge\bf{GIVEN}$

AP = 5,8,11,14..............n

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Number of terms=23

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To find common difference__d

$\tt\large\red\rightarrow$d=8-5

$\tt\large\red\rightarrow$d=3

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a(first term)=5

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$\huge\tt{Answer}$

$\tt\large\red\rightarrow$By using the sum formula__

$\tt\large\red\rightarrow{\frac{n}{2} (2a + (n - 1)a)}$

$\tt\large\red\rightarrow{\frac{23}{2} (2(5) + (23 - 1)5)}$

$\tt\large\red\rightarrow{\frac{23}{2} (10 + 22 \times 5)}$

$\tt\large\red\rightarrow{\frac{23}{2} (120)}$

$\tt\large\red\rightarrow{23\times60}$

$\tt\large\red\rightarrow{1380}$

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$\tt\bold{Thus,</p><p>Sum \:\:of\:\: 23\:\: terms\:\: of</p><p> \:\:AP\:\:(5,8,11,14.......)\:\: Is\:\: </p><p>1380\:\:}$