Answer :
N 1
Remember that
the speed is equal to divide the distance by the time
s=d/t
in this problem
we have
d=100 yd
t=5.1 sec
therefore
Convert the units
1 mile=1,760 yards
1 hour=3,600 seconds
so
d=100 yd=100/1,760 miles
t=5.1 sec=5.1/3,600 hours
Find out the speed
speed=(100/1,760)/(5.1/3,600)
speed=40 miles/hour
N 2
speed=175 miles/hour
speed=d/t
d=speed*t
For t=12 sec -----> convert to hours
1 hour=3,600 sec
12 sec=12/3,600 hours
d=175(12/3,600)
d=0.5833 miles
Convert miles to feet
1 mile=5,280 ft
0.5833 miles=0.5833*5,280=3,080 ft
Convert 12 sec to hours
1 hour=3,600 sec
so
[tex]12\text{ sec=12 sec}\cdot\frac{1}{3,600}\frac{hours}{\sec}=12\sec \cdot\frac{1\text{ hours}}{3,600\text{ sec}}=\frac{12}{3,600}\text{hours}[/tex]