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Problem Solving with Multi-Step Equations

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Basics on the topic Problem Solving with Multi-Step Equations

Learn about solving problems by writing and solving equations.

Transcript Problem Solving with Multi-Step Equations

The seventh graders from Whispering Pines Middle School are going on a field trip to a local theme park. During the field trip, they encounter some problem-solving with multi-step equations. In order to solve the problems given, they must be sure to read carefully to identify keywords and operations. Then, write a let statement to introduce a variable, and translate it, or turn the problem into an equation. Once an equation has been written, it can be solved to identify the solution. Let's look at the first problem the class has to solve. A group of three hundred thirty-one students are going on a field trip to a theme park. Seven of the students rode in cars to get there, but the rest rode in school buses. If each bus can fit fifty-four students, how many buses will they need to get there? The question reveals that the missing information is the number of buses, so let b equal buses. There are bus riders and car riders that combine to be our total. This is the total students, so three hundred thirty-one should be on one side of the equal sign. Seven of the students are riding in cars, so that is a constant. Lastly, if each bus fits fifty-four students, and buses is b, these terms must be multiplied since it is fifty-four students per bus. This equation can be solved, to find that b equals six, which means that the field trip will require six buses. Once at the park, one of the groups decides to ride the roller coaster called Dragon's Breath. Pause the video and read the problem carefully. The group has eleven students in it, and the roller coaster can fit four people in each row. Three are not riding the roller coaster. First, the let statement can identify the missing variable from the question, let r equal rows. Start building the equation with a total of eleven. From eleven, four riders per row can be subtracted. This equals three, which are the remaining students in the group. When the equation is solved it's concluded that the group will occupy two rows on the roller coaster. Let's take a look at the last example. Remember to identify keywords, write a let statement, and then translate the problem into a proper equation. Pause the video and try it on your own. The let statement will be, let f equal friends since the question asks us to find out how many friends got ducks. And the equation can look like this, or this, or this, depending on how you interpreted the word problem. When any of these equations are solved, it's evident that this student has shared the ducks with five friends. Let's summarize problem-solving with multi-step equations. Remember, it is important to read carefully to identify words that will help us translate it into an equation. Also, be sure to write a let statement to introduce the variable we will use. Lastly, translate it into an equation, solve it, and identify the solution. Problem-solving with equations is something that will be useful in life, not only at the theme park, but also when making purchases, preparing meals, and making many everyday decisions. And now that we have solved all these problems, let's go celebrate by riding some more theme park rides!

Problem Solving with Multi-Step Equations exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Problem Solving with Multi-Step Equations.
  • What are the steps when solving problems with multi-step equations?

    Hints
    • Read the word problem carefully to identify any key information first.
    • We can then introduce a variable (for example $a$ or $b$ or any letter).
    • Write down the information using the variable.

    When you have the variable translate it into an equation so you can solve it.

    For example, the cost of a taxi ride = $£3$ for each mile ($m$) plus $£2$ standing charge.

    We would write $C$ = $3m$ + $2$ as an equation.

    Solution
    1. Identify key words and operations.
    2. Introduce a variable and make a statement.
    3. Translate the statement into an equation
    4. Solve the equation.
  • Transfer the statement to an expression.

    Hints

    To change the statement into an expression we are shortening the information.

    For example, $5$ lots of $n$ can be written as $5n$ in short.

    If Maisy is $g$ years old and Molly is $4$ years older, then Molly's age is $g + 4$.

    Solution
    • $3$ more than $a$, we can write as: $a + 3$
    • $3$ lots of $a$, we can write as $3a$
    • $3$ less than $a$, we can write as $a - 3$
    • $3$ times $a$, then add $3$, we can write as $3a + 3$
  • Turn the problem into a formula.

    Hints

    Identify the key words and form a statement.

    Grandma makes $51$ cup cakes.

    Grandpa eats $3$ cakes and the others are put in boxes, ($b$) of $12$.

    • Total cakes is $51$
    • We multiply the boxes, ($b$) by $12$ (as $12$ cakes fit in each box)
    • We need to add $3$ for the ones which were given to Grandpa.
    Solution

    $51 = 12b + 3$

    • Total cakes is $51$
    • We multiply the boxes, ($b$) by $12$ (as $12$ cakes fit in each box)
    • We need to add $3$ for the ones which were given to Grandpa.
  • Solve the multi-step equation.

    Hints
    • Identify the key words and form a statement
    • Let $t$ be Tim's age and form an equation from the statement
    • Solve the equation to find $t$
    • Let Tim's age be $t$
    • Let Tam's age be $t - 2$
    • Translate the statement into an equation
    • $t + t - 2 = 28$
    • Solve the equation
    Solution

    Tim is $15$ years old

    • Let Tim's age = $t$
    • Let Tam's age = $t - 2$
    • $t + t - 2 = 28$
    • Solve for t.
    $2t - 2 = 28$

    $2t = 28 + 2$

    $2t = 30$

    $t = 30 \div 2$

    $t = 15$ years old

  • Solve the multi-step equation.

    Hints

    Identify the keywords and form a statement.

    The gardener charges $£85$ for $£15$ times the hours worked plus $£10$ call out fee.

    Total Charge: $=15\times$ Hours $+ 10$

    Let Hours be $h$

    $85 = 15h + 10$

    $15h + 10 = 85$

    Solve the equation by first subtracting $10$ from both sides.

    $15h = 75$

    $15h = 75$

    Divide by $15$ next.

    Solution
    • Let hours be $h$, $15h + 10 = 85$.
    • Subtract $10$ from both sides, $15h = 75$
    • Divide both sides by $15$, $h = 75 $\div 15$
    • $h = 6$ hours.
  • Solve the multi-step equation.

    Hints

    The perimeter is all the way around the rectangle.

    We add all $4$ lengths together.

    Identify the key words and form a statement.

    Height is $L$.

    Base is $2L + 5$.

    The perimeter (all the way around the rectangle) $ = 52$

    Translate the statement into an equation.

    $L + L + 2L + 5 + 2L + 5 = 52$

    Simplify, then solve the equation.

    Solution

    $\bf{L = 7}$ cm

    Height $ = L$

    Base $ = 2L + 5$

    There are $2$ heights and $2$ bases in the perimeter.

    $L + L + 2L + 5 + 2L + 5 = 52$

    $6L + 10 = 52$

    Subtract $10$ from both sides.

    $6L = 42$

    Divide both sides by $6$.

    $L = 42 \div 6$

    $L = 7$ cm