/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 9 Andrei and his younger brother a... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Andrei and his younger brother are having a race. Because the younger brother can't run as fast, Andrei lets him start out \(5 \mathrm{~m}\) ahead. Andrei runs at a speed of \(7.7 \mathrm{~m} / \mathrm{s}\). His younger brother runs at \(6.5 \mathrm{~m} / \mathrm{s}\). The total length of the race is \(50 \mathrm{~m}\). a. Write an equation to find how long it will take Andrei to finish the race. Solve the equation to find the time. b. Write an equation to find how long it will take Andrei's younger brother to finish the race. Solve the equation to find the time. c. Who wins the race? How far ahead was the winner at the time he crossed the finish line?

Short Answer

Expert verified
Andrei wins the race, finishing approximately 7.81 meters ahead of his brother.

Step by step solution

01

Equation for Andrei's Time

We need to calculate the time it takes for Andrei to complete the race. We use the formula for time, which is \( t = \frac{d}{v} \), where \( t \) is time, \( d \) is distance, and \( v \) is speed. For Andrei, \( d = 50 \) m and \( v = 7.7 \) m/s. Therefore, the equation is \( t = \frac{50}{7.7} \).
02

Solve Andrei's Equation

Now, let's calculate the time using the equation from Step 1. \( t = \frac{50}{7.7} \approx 6.49 \) seconds.
03

Equation for Younger Brother's Time

Now, calculate the time it will take Andrei's younger brother to finish the race. He starts 5 meters ahead, so he only needs to run 50 - 5 = 45 meters. Using the formula \( t = \frac{d}{v} \), we substitute \( d = 45 \) m and \( v = 6.5 \) m/s. The equation is \( t = \frac{45}{6.5} \).
04

Solve Younger Brother's Equation

Using the equation from Step 3, solve for time. \( t = \frac{45}{6.5} \approx 6.92 \) seconds.
05

Determine Winner

Compare the times we calculated: Andrei's time is approximately 6.49 seconds, and the younger brother's time is approximately 6.92 seconds. Andrei finishes the race faster.
06

Calculate Distance Ahead

To find how far ahead Andrei was when he finished, calculate the distance his younger brother had covered in 6.49 seconds at 6.5 m/s. Distance = speed × time = 6.5 m/s × 6.49 s ≈ 42.19 m. Since Andrei ran 50 meters when his brother was at 42.19 meters, Andrei was 50 - 42.19 ≈ 7.81 meters ahead.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Relationship between Distance, Speed, and Time
Understanding the relationship between distance, speed, and time is fundamental in solving problems involving motion, such as running a race. The basic formula to remember is: \[ t = \frac{d}{v} \] where:
  • \( t \) is the time in seconds,
  • \( d \) is the distance in meters, and
  • \( v \) is the speed in meters per second.
This relationship tells us that time is equal to the distance traveled divided by the speed at which you're traveling.
In the race problem, we use this formula to determine how long it takes each runner to finish the race. For Andrei, who runs at 7.7 m/s, covering a distance of 50 meters entails fewer seconds than his younger brother, who runs 45 meters at 6.5 m/s. By applying this crucial formula, you can determine exactly how long it takes each runner to complete their segment of the race.
Problem-Solving Techniques in Mathematics
Effective problem-solving in mathematics often requires breaking a problem down into simpler parts. This systematic approach helps in understanding complex problems and solving them efficiently. Let’s see how it applies to the race problem: First, identify what you need to find: the time taken by both Andrei and his younger brother to complete the race.
Next, apply the distance-speed-time formula to find these times individually.
  • For Andrei: Use the entire race distance of 50 meters with his speed.
  • For his brother: Account for the 5-meter head start, resulting in a reduced race distance of 45 meters.
Finally, after calculating both times, compare them to determine the winner.
Through these steps, we see how mathematics can simplify complex real-world scenarios by systematic thinking and applying relevant equations.
Understanding Race Problems
Race problems often involve competitive scenarios where individuals start from different positions or have different speeds. Here, Andrei and his brother start at different distances and run at different speeds, making it necessary to calculate each runner's time to finish.
  • The younger brother starts 5 meters ahead, impacting his needed distance to the finish line.
  • While Andrei covers the full 50 meters, his brother only needs to cover 45 meters due to his head start.
    This combination of varying initial positions and speeds requires evaluating each contestant separately.
    Such problems illustrate how mathematics helps us analyze competitive situations simply, allowing us to determine outcomes like who wins and by how much distance.
    By understanding the mechanics of race problems, one can apply these skills to assess similar situations where participants have unequal starting points or speeds.
  • One App. One Place for Learning.

    All the tools & learning materials you need for study success - in one app.

    Get started for free

    Most popular questions from this chapter

    Consider the expression $$ \frac{5.4+3.2(x-2.8)}{1.2}-2.3 $$ a. Use the order of operations to find the value of the expression if \(x=7.2\). b. Set the expression equal to \(3.8\). Solve for \(x\) by undoing the sequence of operations you listed in \(11 \mathrm{a}\).

    A multiplicative inverse is a number or expression that you can multiply by something to get a value of 1 . The multiplicative inverse of 4 is \(\frac{1}{4}\) because \(4 \cdot \frac{1}{4}=1\). Give the multiplicative inverse of each number. a. 12 b. \(\frac{1}{6}\) c. \(0.02\) d. \(-\frac{1}{2}\)

    Positive multiples of 7 are generally listed as \(7,14,21,28, \ldots\). a. If 7 is the Ist multiple of 7 and 14 is the 2 nd multiple, then what is the 17th multiple? (a) b. How many multiples of 7 are between 100 and 200 ? (a) c. Compare the number of multiples of 7 between 100 and 200 with the number between 200 and 300 . Does the answer make sense? Do all intervals of 100 have this many multiples of 7? Explain. (a) d. Describe two different ways to generate a list containing multiples of 7 . (a)

    A bicyclist, \(1 \mathrm{mi}(5280 \mathrm{ft})\) away, pedals toward you at a rate of \(600 \mathrm{ft} / \mathrm{min}\) for \(3 \mathrm{~min}\). The bicyclist then pedals at a rate of \(1000 \mathrm{ft} / \mathrm{min}\) for the next \(5 \mathrm{~min}\). a. Describe what you think the plot of (time, distance from you) will look like. (A) b. Graph the data using 1 min intervals for your plot. (a) c. Invent a question about the situation, and use your graph to answer the question.

    Consider the expression \(\frac{4(y-8)}{y}\). a. Find the value of the expression if \(y=5\). Make a table to show the order of operations. (a) b. Solve the equation \(\frac{4(y-8)}{3}=8\) by undoing the sequence of operations. (a)

    See all solutions

    Recommended explanations on Math Textbooks

    View all explanations

    What do you think about this solution?

    We value your feedback to improve our textbook solutions.

    Study anywhere. Anytime. Across all devices.