In Act 3.1 of Shakespeare's Macbeth, Macbeth asks Banquo if he is going riding, how far he's going, and if Fleance is going with him. The reader understands why he asks these questions and what purpose they serve during the next couple of scenes.
These questions are logistical. Macbeth is in the process of planning the murders of Banquo and Fleance with the two murderers he meets with after Banquo exits. If Macbeth is going to know when and where to set the trap, he has to know Banquo's schedule. And if he's going to eliminate any chance of Banquo's heirs ruling Scotland (instead of Macbeth's) then Fleance must be killed too.
The three questions enable Macbeth to set his trap for Banquo and Fleance: a little ways from the castle and a little before the feast Banquo is supposed to attend. The victims will be on foot, having stabled their horses, and be on the path from the stables to the castle.
These three questions are very significant because Macbeth wanted to know about the movement of Banquo. The witches predicted that though Banquo could not be the king himself, he would be father of king. This led to great weariness to Macbeth because Banquo had a son named Fleance. His evil mind hint him that Fleance could be the king of Scotland. So he planed to kill Fleance and make his throne free from any danger.
Macbeth planed to kill them on the way to Macbeth' castle, inviting them for a feast. He even invited Banquo as the chief guest of the feast. But Banquo said that he was going somewhere with his son but return soon to the feast. Having heard this, it became easy for Macbeth to plan their murder and therefore he hired murderer to accomplish the task. The murderers were given special caution that Fleance should not escape at any cost.