Number System

HCF & LCM

Medium

Integer multiples of 3 are arranged in increasing order, starting with 3, such that the difference between $k^{th}$ number in this list and $(k+1)^{th}$ is the LCM of 3 and $k$ . Calculate the sum of the first 5 numbers.

161

✅ Correct Option: 2

The list starts at $a_1 = 3$ , and each next term is given by $a_{k+1} = a_k + \text{LCM}(3, k)$ .

$a_1 = 3$

$a_2 = 3 + \text{LCM}(3,1) = 3 + 3 = 6$

$a_3 = 6 + \text{LCM}(3,2) = 6 + 6 = 12$

$a_4 = 12 + \text{LCM}(3,3) = 12 + 3 = 15$

$a_5 = 15 + \text{LCM}(3,4) = 15 + 12 = 27$

Sum $= 3 + 6 + 12 + 15 + 27 = 63$

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Integer multiples of 3 are arranged in increasing order, starting with 3, such that the difference between kthk^{th}kth number in this list and (k+1)th(k+1)^{th}(k+1)th is the LCM of 3 and kkk. Calculate the sum of the first 5 numbers.

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BMSAT Kozhikode Past Year Questions (Topic-Wise)

Integer multiples of 3 are arranged in increasing order, starting with 3, such that the difference between $k^{th}$ number in this list and $(k+1)^{th}$ is the LCM of 3 and $k$ . Calculate the sum of the first 5 numbers.