JEE Main201911 Jan 2019Evening ShiftMathematicsSequences and SeriesActual

If 19 th term of a non-zero A.P. is zero, then its (49th term): (29th term) is:

Options

A4: 1
B1: 3
C3: 1
D2: 1

Correct answer

C. 3: 1

Step-by-step solution

Let first term and common difference of A P be a and d respectively, then t_ n =a+(n-1) d t₁₉=a+18 d=0 a=-18 d t₄₉ t₂₉ = a+48 d a+28 d = -18 d+48 d -18 d+28 d = 30 d 10 d =3t₄₉: t₂₉=3: 1

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