Question

Goose a variable and write an equation to solve the situation. Kevin drive 320 miles to a mountain resort. His return trip took 20 minutes longer because his speed returning was 4 mr/h slower than his speed going.

Answer 1

• 320/x + 1/3 = 320/(x - 4)
• x = 64 mph

Explanation:

Let the speed is x.

We have equation:

• 320/x + 20/60 = 320/(x - 4) ⇒ 320/x + 1/3 = 320/(x - 4)

To solve we need to get rid of fraction:

• 320(x - 4) + 1/3x(x - 4) = 320x
• x² - 4x - 3840 = 0
• x² - 4x + 4 = 3844
• (x - 2)² = 62²
• x - 2 = 62
• x = 64