Question

In an orchard, there are two parallel rows of fruit trees, one beside the other. In the first row, every fourth tree is a blackberry tree, and in the second row, every sixth tree is a blueberry tree. The first occurrence of the blackberry tree, where there is a blueberry tree just opposite to it, is .

Answer 1

Position of blackberry trees are multiples of $4,$ i.e., $4,8,12,16,20,\mathrm{24...}$

Position of blueberry trees are multiples of $6,$ i.e., $6,12,18,24,30,\mathrm{36...}$

The first occurrence where both the trees' positions are same is ${12}^{th}.$

Alternatively, the least common multiple of $4$ and $6$ is $12.$

$\therefore$ The first occurrence of the blackberry tree where there is a blueberry tree just opposite to it is ${12}^{th}.$