Greta is taking a road trip from Cincinnati to San Francisco. On the first day, she drove 650 miles in 10 hours. On the second day, she got a later start and drove 540 miles in 8 hours. How many miles per hour faster was her average speed the second day? Write your answer as a decimal or a whole number.

Given:

On the first day, she drove 650 miles in 10 hours.

On the second day, she got a later start and drove 540 miles in 8 hours.

To find:

Difference between average speed of second day and first day.

Solution:

We know that,

On the first day, she drove 650 miles in 10 hours.  So, the average speed is

So, the average speed on first day is 65 miles per hour.

On the second day, she got a later start and drove 540 miles in 8 hours.

So, the average speed on second day is 67.5 miles per hour.

Difference between average speed is

Therefore, the average speed on the second day is 2.5 miles per hour is faster than first day.

question:

could we have options?

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional