Question

a diver needs to fix a gas line at the bottom of the bay. his oxygen tank holds enough air for 120 minutes. the job will take 90 minutes. it will take 10 minutes to get to the to the site and 10 minutes to get back to the surface.

Explanation:

Step1: Calculate total time needed

The total time for the dive includes time to get to the site, job time, and time to get back. So total time = 10 (to site) + 90 (job) + 10 (back) = 110 minutes.

Step2: Compare with oxygen time

The oxygen tank lasts for 120 minutes. Since 110 < 120, we check if the time is within the limit. (Or if the question was about whether he has enough, this is the check.)

Answer:

The total time required for the dive (10 + 90 + 10 = 110 minutes) is less than the oxygen tank's duration (120 minutes), so he has enough air. (If the question was to check sufficiency, this is the conclusion. If it was a calculation of total time, the total time is 110 minutes.)