Answer:
The distance cover by Jill is 60 miles
Step-by-step explanation:
Given as :
The speed of Jill to cover the distance D during rush hour = 15 mph
Let The usual time taken to cover D distance = T hour
So, The time taken to travel during rush hour = ( T + 1 ) hour
The speed of Jill to cover the distance D after rush hour = 30 mph
And The time taken to travel after rush hour = ( T - 1 ) hour
Now,According to question
Distance = Speed × Time
Now, For during rush hour
D = 15 × ( T + 1 )
Or, D = 15 T + 15 ........A
Again , For after rush hour
D = 30 × ( T - 1 )
Or, D = 30 T - 30 ..........B
Solving Eq A and B
I.e 15 T + 15 = 30 T - 30
Or, 15 + 30 = 30 T - 15 T
or, 45 = 15 T
∴ T =
I.e T = 3 hour
So, The usual Time taken = T = 3 hour
Put the value of T in eq A
I.e D = 15 T + 15
Or, D = 15 × 3 + 15
∴ D = 60 miles
So, Distance = D = 60 miles
Hence The distance cover by Jill is 60 miles . Answer