Q15 of 24 Page 115

For what value of k are 2k, k+10 and 3k+2 in AP?

If x, y and z are in AP, the differences between consecutive terms will be same


⇒ y – x = z – y


⇒ 2y = x + z


As, k, 2k and k + 10 are the three terms in AP


⇒ 2(2k) = k + 10 + k


⇒ 4k = 2k + 10


⇒ 2k = 10


⇒ k = 5


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