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Learn how to solve various types of word problems involving quadratic equations, such as distance, work rate, and downstream/upstream problems. Includes relevant formulas.
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Applications Involving Quadratic Equations Section 11.4
Types of Word Problems • Types of word Problems • Word Problems that include the formula. • You do not have to remember one or create one. • Distance Word Problems. • D = R * T • Up Stream Down / Stream word problems • Work Rate Problem (Working Together) • New Formula • Up Stream Down Stream word problem.
Word Problems with formulas • Wyatt is tied to one end of a 40-m elasticized (bungee) cord. The other end of the cord is secured to a winch at the middle of a bridge. If Wyatt jumps off the bridge, for how long will he fall before the cord begins to stretch? • Use 4.9t² = s
Word Problems with formulas • 4.9t² = s • 4.9(t)² = 40 • (t)² = 40/4.9 • (t)² = 8.1632653 • t = 2.857 • It will take Wyatt 2.9 seconds before the cord begins to stretch.
Word Problems with formulas • A stone thrown downward from a 100-m cliff travels 51.6 m in 3 seconds. What was the initial velocity of the object if 4.9t² + vot = s.
Word Problems with formulas • 4.9t² + vot = s • 4.9(3)² + vo(3) = (51.6) • 4.9(9) + vo(3) = (51.6) • vo(3) = (51.6) – 4.9(9) • Vo(3) = 51.6 – 44.1 • Vo(3) = 7.5 • Vo = 7.5 / 3 • Vo = 2.5 • The initial velocity of the object was 2.5 m/s
Distance / Rate = Time • During the first part of a trip, Tara drove 120 miles at a certain speed. Tara then drove another 100 miles at a speed that was 10 miles per hour slower. If the total time of Tara's trip was 4 hours, what was the speed on each part of the trip?
Distance / Rate = Time • Equation... The word problem says • If the total time of Tara's trip was 4 hours • T1 + T2 = total time • (120 / x) + (100 / (x - 10)) = 4
D/R = T Upstream / Downstream • Kofi paddles 1 miles upstream and 1 mile back in a total of one hour. The speed of the river is 2 miles per hour. Find the speed of Kofi's paddle-boat in still water.
D/R = T Upstream / Downstream • T1 + T2 = Total Time • [1 / (P-2) ] + [1 / (P+2)] = 1
WORK RATE • How much work can be done in one hour • Algebraic Definition WR = 1 / T • Set – up • The equation will be summing up all the part works and setting them equal to one (one job)
Work Rate Example • Two pipes are connected to the same tank. Working together, they can fill the tank in 4 hours. The larger pipe, working alone, can fill the pool in 6 hours less time than it would take the smaller one. How long would the smaller one take, working alone, to fill the tank?
Work Rate Example • PW 1 + PW2 = 1 • (4 / x) + (4 / [x - 6] ) = 1
HOMEWORK • Section 11.4 • 26, 29, 34, 35, 39, 43, 46