Multiple choice

Two A.P. series have the same common difference. The first term of one of these is -1 and that of the other is -8. Find the difference between their 4th terms.

  1. -1

  2. -8

  3. 7

  4. 9
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The n-th term of an AP is a + (n-1)d. For the 4th term, T4 = a + 3d. The difference between the 4th terms is (a1 + 3d) - (a2 + 3d) = a1 - a2. Given a1 = -1 and a2 = -8, the difference is -1 - (-8) = 7.

AI explanation

The formula for the nth term of an arithmetic progression is a + (n - 1)d. The fourth term of the first series is -1 + 3d and the fourth term of the second series is -8 + 3d. Subtracting the fourth term of the second series from the fourth term of the first series gives (-1 + 3d) - (-8 + 3d) = 7.

Keep practicing — related questions