Significant Figures in Average Velocity Calculation

[michaelplease]

Homework Statement

A rocket traveling at 88 m/s is accelerated uniformly to 132 m/s over a 15.0 second interval. What is its average velocity, with the correct number of significant figures?

An object traveling at 11.5 m/s is decelerated uniformly to 4.5 m/s. What is its average velocity, with the correct number of significant figures?

Homework Equations

v_av=(v_f+v_i)/2

The Attempt at a Solution

1. v_av = (132 m/s + 88 m/s) / 2
= (2.20 * 10^2 m/s) / 2
= 1.10 * 10^2 m/s

After adding the 132 m/s + 88 m/s, would it have 3 significant figures or only 2? It ends in a 0 but I think logically it should still have 3 significant figures, as if you add only 1 m/s to either 132 or 88 you would obviously get 3 significant figures.

Then after dividing it by 2, would one keep the same number of significant figures as v_i + v_f ? or the same decimal places? or the same significant figures or decimal places as v_i or v_f?

2. v_av = (4.5 m/s + 11.5 m/s) / 2
= (16.0 m/s) / 2
= 8.00 m/s

Again, after adding v_i and v_f it ends in a 0. So I imagine it should be 16.0 m/s.

Then when you divide it by 2, would the v_av keep the 3 significant figures, since it is dividing? Or would it have only two, to keep the same decimal places as 16.0 and/or the same sig figs and decimal places as 4.5?

Please help me with this problem and explain to me why that is the correct number of significant figures.

Thank you very much!

 

[PhanthomJay]

Yes, logically the first part has 3 sig figs, but part 2 has just 2 (16.0/2 =8.0), accurate to one figure after the decimal point.