Answer: 11 minutes approximately
=================================================
Explanation:
Let's calculate the time taken to drive at 100 km/hr
distance = rate*time
time = distance/rate
time = 160/100
time = 1.6 hours exactly
Do the same for when she drove at 90 km/hr
time = distance/rate
time = 160/90
time = 1.7778 hours approximately
------------------
Next, subtract the time values
1.7778 - 1.6 = 0.1778
The difference in time values is about 0.1778 hours.
------------------
The last step is to multiply by 60 to convert from hours to minutes.
0.1778*60 = 10.668
This then rounds to 11 minutes
