Question

One morning, Justin drove 3 hours before stopping to eat lunch at Chick-fil-A. After lunch, he increased his speed by 10 mph. If he completed a 530-mile trip in 8 hours of driving time, how fast did he drive in the morning?

Answer 1

60 miles per hour

Explanation:

Let x represent Justin's speed in the morning.

We have been given that one morning Justin drove 3 hours before stopping to eat lunch at Chick-fil-A.

`\text{Distance}=\text{Speed}* \text{Time}`

Distance covered by Justin in 3 hours would be
`3x`.

After lunch, he increased his speed by 10 mph; so his new speed would be
`x+10`.

We are also told that he traveled 530-mile trip in 8 hours. The time he drove after lunch would be
`8-3=5\text{ hours}`.

Distance covered by Justin in 5 hours after lunch would be
`5(x+10)`.

Now, we will equate distance traveled before and after lunch to solve for x as:

`3x+5(x+10)=530`

`3x+5x+50=530`

`8x+50=530`

`8x+50-50=530-50`

`8x=480`

`(8x)/(8)=(480)/(8)`

`x=60`

Therefore, Justin drove at a speed of 60 miles per hour in the morning.