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Evaluating expressions with variables word problems

Learn to evaluate expressions in word problems to gain new information. 
Khan Academy video wrapper
Evaluating an expression with one variableSee video transcript

Reflection question

What was Sal finding when he plugged t, equals, 10 into the expression 5, t, plus, 3?
Choose 1 answer:

Let's try a practice problem!

The expression 2, m, plus, 10, c gives the amount of money, in dollars, a dessert store makes from selling m muffins and c cakes.
How much money does the dessert store make from selling three muffins and four cakes?
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text
dollars

Challenge problem

Part A
A flower store uses the expression 2, plus, 5, r to determine the cost, in dollars, of r roses.
Complete the table to find the cost of different numbers of roses.
Number of roses left parenthesis, r, right parenthesisCost left parenthesis, 2, plus, 5, r, right parenthesis
317
6
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text
9
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text

Part B
Cam has 32 dollars. How many roses can he afford to buy?
Assume that he wants to buy as many roses as he can.
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text

Extra challenge

Explain to a family member, friend, or classmate why the cost of six roses is not double the cost of three roses.

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