Question

Cedric and Insha solved the same equation using the calculations below.

Cedric’s Work
Insha’s Work
z minus 4.5 = negative 1.5. z minus 4.5 + 4.5 = negative 1.5 + 4.5. z = 3.
z minus 4.5 = negative 1.5. z minus 4.5 + (negative 4.5) = negative 1.5 + (negative 4.5). z = negative 6.

Which statement is true about their work?
Cedric is correct because he used the inverse of subtraction and added 4.5.
Cedric is incorrect because he should have subtracted 4.5 from both sides instead of adding.
Insha is correct because she added the opposite if 4.5, which is Negative 4.5, to both sides.
Insha is incorrect because she did not add Negative 1.5 + (negative 4.5) correctly.

Answer 1

(a) Cedric is correct because he used the inverse of subtraction and added 4.5

Explanation:

You want to know if Cedric's work or Insha's work is correct in solving the equation ...

• z - 4.5 = -1.5

Solution

The equation is solved by adding the opposite of -4.5 to both sides:

z - 4.5 + 4.5 = -1.5 + 4.5

z = 3 . . . . . . . . . . simplified

This matches Cedric's work.

Cedric is correct because he used the inverse of subtraction and added 4.5, option A.

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Additional comment

Insha's work should end as ...

z -9 = -6

She failed to properly simplify the left side of her equation after subtracting 4.5 from both sides. Had she done that simplification properly, she would easily identify her error.

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