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