Lisa started to drive from Boston to Washington, DC, which is 440 miles away, at 8:00 AM. For the first four hours of her trip, Lisa was driving at a speed of 50 mph. What was her average speed during the second part of the trip, if she reached Washington at 4:00 PM?

60 mph

Step-by-step explanation:

Given;

Total distance covered d = 440 miles

Average speed in the first 4 hours v1 = 50 mph

Total time taken for the whole trip t = 8:00 to 4:00pm

t = 16:00-8:00 = 8 hours

Firstly we need to calculate the distance covered during the first 4 hours;

d1 = average speed × time = v1 × t1

t1 = 4

d1 = 50 × 4 = 200 miles

Then we need to calculate the distance covered in the second period of the journey;

d = d1 + d2

d2 = d - d1

Substituting the values;

d2 = 440 - 200

d2 = 240 miles

The time taken for the second period of travel t2;

t2 = t -t1 = 8-4

t2 = 4 hours

Average speed = distance travelled ÷ time taken

The average speed for the second part of the trip v2 is;

v2 = d2 ÷ t2

Substituting t2 and d2;

v2 = 240 miles ÷ 4 hours

v2 = 60 mph

The average speed during the second part of the trip is 60 mph

see explanation

step-by-step explanation:

since the sequence is geometric there is a common ratio r between consecutive terms, that is

r = 4 ÷ - 2 = - 2

r = - 8 ÷ 4 = - 2

r = 16 ÷ 8 = - 2

the next term - 13 must be incorrect as it should be - 32 for the sequence to be geometric.

the first 4 terms are therefore geometric with common ratio r = - 2

it could be 1,3 and more others to create a cylinder.

step-by-step explanation: