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Set up and solve an appropriate system of linear equations to answer the questions. The sum of Annie's, Bert's, and Chris's ages is 60 Annie is older than Bert by the same number of years that Bert is older than Chris. When Bert is as old as Annie is now, Annie will be three times as old as Chris is now. What are their ages? The preceding two problems are typical of those found in popular books of mathematical puzzles. However, they have their origins in antiquity. A Babylonian clay tablet that survives from about 300 s.c. contains the following problem.

Short Answer

Expert verified
Annie is 28 years old, Bert is 20 years old, and Chris is 12 years old.

Step by step solution

01

Define Variables

Let's define the variables for the ages of Annie, Bert, and Chris. Let \( A \) be Annie's age, \( B \) be Bert's age, and \( C \) be Chris's age.
02

Set Up Equations from Sum of Ages

According to the problem, the sum of Annie's, Bert's, and Chris's ages is 60. This gives us our first equation:\[ A + B + C = 60 \]
03

Formulate Equation for Age Difference

Annie is older than Bert by the same number of years that Bert is older than Chris. This means:\[ A - B = B - C \]Simplifying, we get:\[ A - 2B + C = 0 \]
04

Future Age Condition

When Bert is as old as Annie is now, Annie will be three times as old as Chris is now. This condition can be expressed as:\[ A + (A - B) = 3C \]Simplifying gives:\[ 2A - B = 3C \]
05

Solve the System of Equations

We now have the following system of equations:1. \( A + B + C = 60 \)2. \( A - 2B + C = 0 \)3. \( 2A - B = 3C \)Let's solve these equations step by step. From equation (2), \( A = 2B - C \). Substitute \( A \) into equations (1) and (3).Equation (1):\[(2B - C) + B + C = 60 \Rightarrow 3B = 60 \Rightarrow B = 20 \]Equation (2) simplifies \( B = 20 \) and solving for \( A \) or \( C \) gives further the needed values.
06

Compute Individual Ages

With \( B = 20 \), substitute back into equation from step (2):\[ A = 2(20) - C \Rightarrow A = 40 - C \]Substituting \( A = 40 - C \) into equation (3) gives:\[ 2(40 - C) - 20 = 3C \]\[ 80 - 2C - 20 = 3C \]\[ 60 = 5C \]\[ C = 12 \]Substituting \( C = 12 \) into \( A = 40 - C \):\[ A = 40 - 12 \Rightarrow A = 28 \]Therefore, the ages are \( A = 28 \), \( B = 20 \), \( C = 12 \).

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Key Concepts

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

Age-Related Problems
Age-related problems in mathematics are excellent brain teasers and exercises to practice logical thinking. These problems usually involve the ages of multiple people and how they relate to each other. They require setting up relationships and conditions based on age differences and sums.

In this specific exercise, we deal with three individuals: Annie, Bert, and Chris. Their ages have a certain sum, and there are conditions relating these ages to each other in different ways.
  • The total sum of their ages is given.
  • Differences in their ages are described.
  • There is a future condition based on their ages, comparing how their ages progress over time.
Using these details, we can form equations that express these relationships and solve them systematically to find the ages of each person.
Linear Equations
Linear equations are mathematical expressions that represent relationships between variables using equality. These involve expressions where each variable is raised to the first power and combined through addition or subtraction.

In our problem, there are three equations developed from given conditions:
  • Sum of ages: \( A + B + C = 60 \)
  • Age difference condition: Annie is as many years older than Bert as Bert is older than Chris, represented as \( A - 2B + C = 0 \).
  • Future age comparison: When Bert reaches Annie’s current age, Annie will be three times as old as Chris is now, given by \( 2A - B = 3C \).
These equations form the backbone of our calculations. To solve such a system, we can use methods like substitution, elimination, or matrix operations to find the values of variables that satisfy all the equations simultaneously.
Problem-Solving Steps
Solving age-related problems involves a sequence of logical problem-solving steps. Here's a simple breakdown of these steps to guide through the process:

1. **Define the Variables:** Clearly start by determining what each variable represents, such as \( A \) for Annie's age, \( B \) for Bert's age, and \( C \) for Chris's age.
2. **Translate Conditions into Equations:** Use the problem details to form equations. For example:
  • The sum of their ages forms one equation.
  • Age differences yield another equation.
  • Future conditions give a third equation.
3. **Solve the Equations Systematically:** Use substitution or elimination to isolate one variable and find its value. Substitute this back into other equations to find the remaining variables.
4. **Verify the Solution:** Once you reach a solution, check that these values satisfy all original conditions and adjustments given in the problem to ensure accuracy.

These structured steps make it easier to navigate even complex age-related puzzles and ensure consistency in finding the solution. Understanding these can help solve not just this problem, but many others structured in a similar manner.

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Most popular questions from this chapter

A coffee merchant sells three blends of coffee. A bag of the house blend contains 300 grams of Colombian beans and 200 grams of French roast beans. A bag of the special blend contains 200 grams of Colombian beans, 200 grams of Kenyan beans, and 100 grams of French roast beans. A bag of the gourmet blend contains 100 grams of Colombian beans, 200 grams of Kenyan beans, and 200 grams of French roast beans. The merchant has on hand 30 kilograms of Colombian beans, 15 kilograms of Kenyan beans, and 25 kilograms of French roast beans If he wishes to use up all of the beans, how many bags of each type of blend can be made?

Solve the given system of equations using either Gaussian or Gauss-Jordan elimination. $$\begin{aligned} \frac{1}{2} x_{1}+x_{2}-x_{3}-6 x_{4} &=2 \\ \frac{1}{6} x_{1}+\frac{1}{2} x_{2} &-3 x_{4}+x_{5}=-1 \\ \frac{1}{3} x_{1} &-2 x_{3}-4 x_{5}=8 \end{aligned}$$

For what value(s) of \(k,\) if any, will the systems have (a) no solution, (b) a unique solution, and (c) infinitely many solutions? $$\begin{aligned} x+y+k z &=1 \\ x+k y+z &=1 \\ k x+y+z &=-2 \end{aligned}$$

Set up and solve an appropriate system of linear equations to answer the questions. The process of adding rational functions (ratios of polynomials by placing them over a common denominator is the analogue of adding rational numbers. The reverse process of taking a rational function apart by writing it as a sum of simpler rational functions is useful in several areas of mathematics; for example, it arises in calculus when we need to integrate a rational function and in discrete mat hematics when we use generating functions to solve recurrence relations. The decomposition of a rational function as a sum of partial fractions leads to a system of linear equations. Find the partial fraction decomposition of the given form. (The capitall) letters denote constants. $$\begin{array}{l} \frac{x-1}{(x+1)\left(x^{2}+1\right)\left(x^{2}+4\right)} \\ =\frac{A}{x+1}+\frac{B x+C}{x^{2}+1}+\frac{D x+E}{x^{2}+4} \end{array}$$

A florist offers three sizes of flower arrangements containing roses, daisies, and chrysanthemums. Each small arrangement contains one rose, three daisies, and three chrysanthemums. Each medium arrangement contains two roses, four daisies, and six chrysanthemums. Each large arrangement contains four roses, eight daisies, and six chrysanthemums. One day, the florist noted that she used a total of 24 roses, 50 daisies, and 48 chrysanthemums in filling orders for these three types of arrangements. How many arrangements of each type did she make?

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