How to write basic algebraic expressions from word problems | 6th grade | Khan Academy

TL;DR

Learn how to write expressions for word problems by understanding the relationship between variables and using multiplication, division, and addition.

Transcript

• Let's do a few examples of writing expressions to help us solve word problems. So they tell us Susie ran a race. She ran five miles an hour, and the race took her t hours to complete. How long was the race? Write your answer as an expression. Alright, if we're trying to figure out the number of miles, you'd want to take her speed, which is in mil... Read More

Key Insights

• 😑 Expressions in word problems involve representing mathematical relationships between variables and quantities.
• ✖️ Multiplication is used to represent quantities that are multiplied together, such as speed and time.
• ➗ Division is used to represent quantities that are divided, such as money divided among people.
• 🪐 Subtraction is used to calculate net values, such as winnings after deducting expenses.
• #️⃣ Addition is used to combine quantities, such as the total number of items made or collected.
• 😑 Understanding the context of the problem is crucial to determine the appropriate operations and relationships to include in the expressions.
• 🤔 Practicing writing expressions for word problems helps develop problem-solving and algebraic thinking skills.

Questions & Answers

Q: How do you write an expression for the distance in a word problem involving speed and time?

To write an expression for the distance, multiply the speed (in miles per hour) by the time (in hours). For example, if the speed is 5 mph and the time is t hours, the expression would be 5t.

Q: How do you write an expression for dividing a certain amount of money among a number of people?

To write an expression for dividing money among a number of people, use the division symbol. For example, if $548 is divided among p players, the expression would be 548/p.

Q: How do you calculate net winnings in a word problem involving prize money and entry fees?

To calculate net winnings, subtract the amount spent (such as entry fees) from the prize money. For example, if Phil won x dollars but spent $100 to enter the tournament, the expression representing his net winnings would be x - 100.

Q: How do you find the total number of items in a word problem involving different types of items?

To find the total number of items, add the quantities of each type. For example, if Hillary made 48 chocolate chip cookies and y sugar cookies, the expression representing the total number of cookies would be 48 + y.

Summary & Key Takeaways

• Writing expressions for word problems involves identifying the variables and their relationships, and using mathematical operations to represent the problem.

• For example, if Susie ran a race at a speed of 5 miles per hour for t hours, the expression representing the distance she ran would be 5t.

• In another example, if $548 winnings were split evenly among p players, the expression representing how much money each player received would be 548/p.