Ruben is driving along a highway that passes through Barstow. His distance d, in miles, from Barstow is given by the equation
d = |210 − 60t|,
where t is the time, in hours, since the start of his trip and
0 ≤ t ≤ 5.
When will Ruben be exactly 90 miles from Barstow? (Enter your answers as a comma-separated list.)

Respuesta :

The absolute value of a number returns the positive value of the given number. Ruben will be at exactly 90 miles in 2 hours or 5 hours

Given that:

[tex]d = |210 - 60t|[/tex]

To calculate t when [tex]d = 90[/tex], we have:

[tex]90 = |210 - 60t|[/tex]

Rewrite as:

[tex]|210 - 60t| = 90[/tex]

Remove absolute bracket

[tex]210 - 60t = 90 \ or\ 210 - 60t = -90[/tex]

Collect like terms

[tex]- 60t = -210 + 90 \ or\ - 60t = -210 -90[/tex]

[tex]- 60t = -120 \ or\ - 60t = -300[/tex]

Divide through by -60

[tex]t = 2 \ or\ t = 5[/tex]

Hence, Ruben will be at exactly 90 miles in 2 hours or 5 hours

Read more about absolute values at:

https://brainly.com/question/1301718