Q1.7 Zero significant digits. An order-of-magnitude calculation is accurate only within a factor of 10.Q1.8 With one datum known to one significant digit, we have 80 million yr + 24 yr = 80 million yr.Q1.9 No, the magnitude of the displacement is always less than or equal to the distance traveled. If twodisplacements in the same direction are added, then the magnitude of their sum will be equal to thedistance traveled. Two vectors in any other orientation will give a displacement less than thedistance traveled. If you first walk 3 meters east, and then 4 meters south, you will have walked atotal distance of 7 meters, but you will only be 5 meters from your starting point.Q1.10 Only force and velocity are vectors. None of the other quantities requires a direction to be described.Q1.11 If the direction-angle ofrAis between 180 degrees and 270 degrees, its components are bothnegative. If a vector is in the second quadrant or the fourth quadrant, its components have oppositesigns.