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The 4th and 7th term of an arithmetic progression are 11 and -4 respectively. What is the 15th term?

A. -49

B. -44

C. -39

D. -34

Answer: Option B

Solution(By Examveda Team)

Let the first term of an AP = a and the common difference = d
4th term of AP = A4 = a + 3d =11 ......(1)
7th term = A7 = a + 6d = -4 ......(2)
Subtracting equation (1) from (2), we get :
⇒ 6d - 3d = -4 -11
⇒ 3d = -15
⇒ d = $$\frac{{ - 15}}{3}$$ = -5
Substituting it in equation (1)
⇒ a = 11 - 3(-5) = 11 + 15 = 26
∴ 15th term = A15 = a + 14d
= 26 + 14(-5)
= 26 - 70
= -44

This Question Belongs to Arithmetic Ability >> Progressions

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