Question

If the common difference of an AP is 5, then what is a18 - a13?(A) 5 (B) 20 (C) 25 (D) 30NCERT Class XMathematics - Exemplar ProblemsChapter _ARITHMETIC PROGRESSIONS

Answer 1

"If d=3 then A15 will be = a + 14d

Similarly A9 will be + a + 8d,

So A15-A9 will be = 6d or 18 (d = 3)

Since d=3 then we need to solve it as a15=a+14d and a9 =a+8d.

Putting the equation (a+14d) - (a+8d) = 14d - 8d = 6d (6×3=12)

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