Question

Two cars start at the same point and travel in opposite directions. The first car travels 15 miles per hour faster than the second car. In 4 hours, the cars are 300 miles apart. Use the formula below to determine the rate of the second car. 4(r + 15) + 4r = 300 What is the rate, r, of the second car? Solve for r.

Answer 1

The rate of the second car is 30 miles/hour

Explanation:

The Given formula is:

4(r + 15) + 4r = 300, where r is the rate for the second car

Let us solve the equation to find r

→ Multiply 4 by (r + 15) first

∵ 4(r + 15) = 4(r) + 4(15) = 4r + 60

→ Substitute it in the equation above

∴ 4r + 60 + 4r = 300

→ Add the like terms in the left side

∵ (4r + 4r) + 60 = 300

∴ 8r + 60 = 300

→ Subtract 60 from both sides

∴ 8r + 60 - 60 = 300 - 60

∴ 8r = 240

→ Divide both sides by 8

∴
`(8r)/(8)=(240)/(8)`

∴ r = 30

∴ The rate of the second car is 30 miles/hour