To determine how far apart A and B will be 45 minutes before they meet, we can use the relative speed concept.
The relative speed of A and B when moving towards each other is the sum of their individual speeds. In this case, it is 80 km/h+40 km/h=120 km/h80km/h+40km/h=120km/h.
Now, we need to find the distance they cover in 45 minutes (0.75 hours). The formula for distance is given by:
Distance=Speed×TimeDistance=Speed×Time
So, the distance they will cover is:
Distance=120 km/h×0.75 hDistance=120km/h×0.75h
Distance=90 kmDistance=90km
Therefore, they will be 90 kilometers apart exactly 45 minutes before they meet.