Math Problem Statement

Leia performed the following calculations. 2+3x4=2+12=14 and 2(3+4)=14 From this she concluded that if a,b,c are whole numbers, then a+bc=a(b+c). How do you respond?

Solution

Leia's conclusion is incorrect due to a misunderstanding of how arithmetic operations work, particularly the difference between addition and multiplication. Here’s why:

  1. Order of operations (PEMDAS/BODMAS): When dealing with expressions like a+bca + bc, multiplication takes precedence over addition. This means a+bca + bc should be interpreted as a+(b×c)a + (b \times c), not (a+b)×c(a + b) \times c.

    • In the first case, Leia correctly applied the order of operations: 2+3×4=2+12=142 + 3 \times 4 = 2 + 12 = 14. Multiplication happens before addition.

    • In the second case, she applied the distributive property: 2(3+4)=2×7=142(3 + 4) = 2 \times 7 = 14, which is correct for multiplication over addition inside parentheses.

  2. Why a+bca(b+c)a + bc \neq a(b + c): These two expressions represent entirely different operations:

    • a+bca + bc means aa plus the product of bb and cc.
    • a(b+c)a(b + c) means aa times the sum of bb and cc.

    These will generally yield different results. For example, if a=2a = 2, b=3b = 3, and c=4c = 4:

    • a+bc=2+(3×4)=2+12=14a + bc = 2 + (3 \times 4) = 2 + 12 = 14,
    • a(b+c)=2×(3+4)=2×7=14a(b + c) = 2 \times (3 + 4) = 2 \times 7 = 14.

    In this specific case, they both equal 14, but this is coincidental. In general, they will give different results.

A Counterexample to Disprove the Conclusion:

If a=2a = 2, b=1b = 1, and c=3c = 3:

  • a+bc=2+(1×3)=2+3=5a + bc = 2 + (1 \times 3) = 2 + 3 = 5,
  • a(b+c)=2×(1+3)=2×4=8a(b + c) = 2 \times (1 + 3) = 2 \times 4 = 8.

Since 585 \neq 8, we see that a+bca(b+c)a + bc \neq a(b + c) in general.

Conclusion:

Leia’s reasoning is based on an example where the expressions happened to give the same result, but this does not hold true for all whole numbers aa, bb, and cc. The correct relationship is a+bca(b+c)a + bc \neq a(b + c) in general.


Would you like more details, or have any further questions?

Related Questions:

  1. Can you provide more examples where a+bca(b+c)a + bc \neq a(b + c)?
  2. How does the distributive property of multiplication over addition work?
  3. What is the difference between commutative and associative properties?
  4. Can parentheses change the result of mathematical expressions involving addition and multiplication?
  5. How can I properly apply the order of operations in more complex expressions?

Tip:

Always remember to follow the order of operations (PEMDAS/BODMAS) to avoid miscalculations.

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Math Problem Analysis

Mathematical Concepts

Algebra
Order of Operations (PEMDAS/BODMAS)
Distributive Property

Formulas

a + bc
a(b + c)
PEMDAS/BODMAS rule

Theorems

Distributive Property of Multiplication Over Addition

Suitable Grade Level

Grades 6-8