Question
The 4th term of an AP is 17 and the 9th term is 42. Find
the sum of the first 20 terms.Solution
ATQ,
d = (42 – 17) / 5 = 5 a = 17 – 3×5 = 2 S20 = 10 × (2×2 + 19×5) = 10 × 99 = 990
More Arithmetic Progression Questions
251, 130, 274, ?, 301, 76Â
14, 17, 23, 32, ?, 59
18, 30, 54, 90, 138, ?
What will come in place of the question mark (?) in the following series?
18, 22, 34, 70, 178, ?
7   4   5   9   20    ?    160.5
4, 4, 12, 60, ?, 3780
12, 14, 20, 32, ?, 82Â
What will come in place of the question mark (?) in the following series?
45, 68, 114, 183, 275, ?
What will come in place of the question mark (?) in the following number series?
21, 42, 67, 96, ?, 166
What will come in place of the question mark (?) in the following series?
4, 2605, 5309, 8118, ?
