Answer:
The estimate rounded to the nearest one-tenth of a second is 66.6 seconds
Explanation:
To find the total time T for all of the four races, we sum the time of each race.
So T = 18.04+21.39+12.99+14.14 = 66.56 seconds.
Now we have to round to the nearest one-tenth of a second, which is the first decimal value.
If the second digit was between 0 and 5(it means 66.50, 66.51, 66.52, etc) the total time would be rounded to 66.5 seconds
Since the second digit is 6, the time is rounded to 66.6 seconds.