Page 896 - Algebra 1

Sometimes there are so many numbers in a problem that it can be confusing to solve. To solve a simpler problem, rewrite the numbers so they are easier to compute.
Writing a Simpler Problem to Solve a Problem
In a cycling race, Elio cycled 128 blocks. One block is 1.9 kilometers. If Elio finished in 5.9 hours, what was his average speed?
Understand
Find Elio’s average speed.
• Distance: 128 blocks each 1.9 km long • Time: 5.9 hours
Plan
Find Elio’s average speed by using simpler numbers to compute.
Example
5
Solve
(128)(1.9)
= (128)(2 - 0.1)
= 128(2) - 128(0.1) = 256 - 12.8
= 243.2 km
d = rt _243.2 = r(5.9)
243.2 ≈ 41.2 km/hr 5.9
Find the total distance of the race. Write 1.9 as 2 - 0.1.
Use the Distributive Property.
Use the distance formula. Solve for r.
Elio’s average speed was about 41.2 km/hr.
Check
Each block is close to 2 miles and 128 is close to 130. The total distance rounds to 260 kilometers.
Round the time to 6 hours and divide into the distance. 260 ÷ 6 ≈ 43.3 km/hr. This is close to 41.2 km/hr.
Skills Bank Practice
a. Frank walked 9 laps around the track. One lap is 1312 feet. Frank walked at a rate of 4 mi/hr. How many minutes did it take him to walk 9 laps?
Skills Bank 881
SKILLS BANK