Work and Rate Problems in Algebra

A military jet flies 1,476 miles. If the plane travels at a speed of s mph and there is a tailwind speeding it up by 18 mi/h, which expression represents the time the flight takes?

• 18 / (s + 1476)

• 18 / (1476 - s)

• 1476 / (s + 18)

• 1476 / (s - 18)

A runner ran 5,000 feet at a rate of x feet per hour. She then ran an additional 8,000 feet at a rate of 6 feet less than twice the first rate. Which expression represents the total number of hours ran?

• 13,000 / (2x - 6)

• 5,000 / x + 8,000 / (2x - 6)

• 13,000(2x - 6)

• 5,000 / x + 8,000 / 2x - 6

A canoer goes 4 miles upstream against a current. He then travels 4 miles downstream with the current. If he travels at 6 mi/h and c is the speed of the current, what is the total time of the trip?

• 4 / (-6c) + 4 / (6c)

• 4 / c + 6 / c

• 2(4 / (6 + c))

• 4 / (6 - c) + 4 / (6 + c)

TechMore can build a computer in t hours. ChipsRus can build a computer in 3 fewer hours. Which expression represents the amount of work completed in 1 hour if they work together?

• 1/t + 1/(t - 3)

• 1/t + 1/3

• 1/t - 1/3

• 1/t - 1/(t - 3)