Question

Desrina travels 70 miles at an average speed of 70 mph.

She then travels a further 70 miles.
The average speed for the entire journey is 57 mph.
Assuming Desrina didn't stop, what was her average speed for the final 70 miles to 2 dp?

Answer 1

its 48.07

Explanation:

be smart

Answer 2

Total miles = 70 + 70 = 140 miles

Total time = 140 miles / 57 mph = 2.456 hours

Time 1: 70 miles / 70 mph = 1 hour

Time 2: 70 miles / x mph

Total time = time 1 + time 2:

2.456 = 1 hour + 70/x

Subtract 1 hour from both sides:

1.456 = 70x

multiply both sides by x:

1.456x = 70

Divide both sides by 1.456:

x = 70/1.456

x = 48.0769 miles per hour

Rounded to 2 dp = 48.08 miles per hour