Question

maths ssc In a.p. 19th terms is 52 and 38th terms is 128 ' find sum of first 56 terms

Answer 1

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Answer 2

Tn = a +<n-1>d

T19= a+18d

52=a+18d.......1

T38=a+37d

128=a+37d........2

Subtracting equation 1from2

We get

19d = 76

d= 76/19

d = 4

Substitute d = 4in equation 1 we get a =-20

Then find the s56

S56 = n/2×a<n-1>d

Substitute the value and. Find yha ans

Ans is s56 = 228