Fran would like to estimate the mean amount of time it takes people in her town to travel to work and towns population is 150000 and about 90,000 of those are working adults

The mean amount of time it takes people in her town to travel to work and towns = (t₁+t₂) / 2

Step-by-step explanation:

Total population is 150000

Adult population is 90,000

The population for the old and kids will be 15000-90000=60000

Assume distance to town is D

Assume the speed taken by adults to travel to town is S₁ and that of the remaining group is S₂, then the time taken for travel will be;

Adults=D/S₁=t₁

Others = D/S₂=t₂

The mean amount of time it takes people in her town to travel to work and towns = (t₁+t₂) / 2

Know the values for D, S₁ and S₂ to get the average time.