Question

Myra is evaluating the expression –31.7 + 4.5x, when x = 2.1.     –31.7 + 4.5(2.1) –27.2(2.1) –57.12 What was Myra’s error?

Answer 1

Myra should have multiplied 4.5 and 2.1 first.

Answer 2

Myra's Error: Addition instead of multiplication

Correct answer: -22.25

Explanation:

Myra is evaluating the expression.

Expression: -31.7 + 4.5x for x=2.1

Step 1: Put x=2.1 into expression

Myra's Steps Correct Step

-31.7 + 4.5(2.1) -31.7 + 4.5(2.1)

Thus, first step correct.

Step 2: Simplify 4.5(2.1) by multiply

Myra's Steps Correct Step

-27.2(2.1) -31.7 + 9.45

Thus, second step incorrect.

Therefore, Myra's error in second step. She did addition(-31.7+4.5) instead of multiplication(4.5×2.1)

Step 3: Combine like terms

-31.7 + 9.45 = -22.25

Hence, The correct answer of the given expression is -22.25