#### Answer

The surveyed adults had a mean of around $1.6$ hours of vigorous activity per week.

#### Work Step by Step

To find the weighted mean, perform the following steps:
(1) Add the frequencies to find the total number of adults.
(2) For each row, multiply the number of hours per week by the number of adults.
(3) Add the results in Step (2).
(4) Divide the result in Step (3) by the result in Step (1)
(Refer to the attached table below.)
Thus, the weighted mean is:
$=\dfrac{791}{500} \approx 1.6$