The problem describes two vertical pipes that are not parallel. The angles formed by a connecting line between the pipes and each pipe are given as 106° and 78°. The goal is to determine how much the second pipe must be moved (rotated) to make it parallel to the first pipe.

1. Problem Description

The problem describes two vertical pipes that are not parallel. The angles formed by a connecting line between the pipes and each pipe are given as 106° and 78°. The goal is to determine how much the second pipe must be moved (rotated) to make it parallel to the first pipe.

2. Solution Steps

Let's denote the angle at Pipe 1 as $A = 106^\circ$ and the angle at Pipe 2 as $B = 78^\circ$. If the two pipes are parallel, then the angles $A$ and $B$ should be supplementary. This means that the sum of the angles should be $180^\circ$. Let $x$ be the angle we need to add or subtract from angle $B$ to make the pipes parallel. Then either $A = 180^\circ - B - x$ or $A = 180^\circ - B + x$. If the pipes are parallel, the angles should be supplementary.

Let's consider the angles formed by the connecting line and the pipes. If the pipes were parallel, these angles would be supplementary, adding up to $180^\circ$. Currently, the sum of the angles is $106^\circ + 78^\circ = 184^\circ$.

Therefore, the difference from $180^\circ$ is:

$184^\circ - 180^\circ = 4^\circ$.

This difference represents the amount by which the angle at Pipe 2 must be adjusted. To make the pipes parallel, we need to reduce the angle at Pipe 2 by $4^\circ$.

3. Final Answer

The second pipe must be moved by subtracting $4^\circ$ to make the pipes parallel.