Question

You drive 6.0 km at 50 km/h and then another 6.0 km at 90 km/h. Your average speed over the 12 km drive will be ____

(A) a greater than 70 km/h.
(B) less than 70 km/h.
(C) exactly 38 km/h.
(D) It cannot be determined from the information given because we must also know directions traveled.
(E) equal to 70 km/h.

Answer 1

The average speed is less than 70 km/h.

(B) is correct option.

Step-by-step explanation:

Given that,

distance = 6.0 km

Speed = 50 km/h

Speed = 90 km/h

We need to calculate the time in 6.0 km distance

Using formula of time

`t = (d)/(v)`

Put the value in to the formula

`t=(6.0)/(50)`

`t=0.12\ hr`

We need to calculate the time in another distance

Using formula of time

`t = (d)/(v)`

Put the value in to the formula

`t=(6.0)/(90)`

`t=0.067\ hr`

We need to calculate the average speed

Using formula of average speed

`v=(D)/(T)`

Where, D = total distance

T = total time

Put the value into the formula

`v=(12)/(0.12+0.067)`

`v=64.17\ km/hr`

Hence, The average speed is less than 70 km/h.