Math, asked by lolexe, 1 month ago


the sum of 5th term and 16th term of an arithmetic sequence is 50. Find the sum of the first 20 terms

Answers

Answered by spiderman2019
0

Answer:

Step-by-step explanation:

nth term of AP is given as tₙ = a + (n-1)d

5th term, t₅ = a + 4d

16th term t₁₆ = a + 15d

given,

t₅ + t₁₆ = 50

=> a + 4d + a + 15d  = 50

=> 2a + 19d = 50 ------------- (1)

Sum to n terms of AP, Sₙ = n/2[ 2a + (n-1)d]

=> S₂₀ = 20/2[ 2a + 19d]

           = 10 * 50  (∵  from (1))

          = 500

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