Question

Anna calculated the area of parallelogram with a base of 72

5
m and a height of 2 m. Her work is shown here.

A = One-half b h = one-half (7 and two-fifths) (2) = one-half (StartFraction 35 Over 5 EndFraction) (StartFraction 2 Over 1 EndFraction) = StartFraction 70 Over 10 EndFraction = 7 meters squared

What errors did the student make? Select all that apply.
She used the incorrect area formula.
She substitute the values for the base and height incorrectly.
She converted the mixed number to an improper fraction incorrectly.
She multiplied incorrectly.
She simplified the fraction StartFraction 70 Over 10 EndFraction incorrectly.

Answer 1

B) She converted the mixed number to an improper fraction incorrectly.

C) She multiplied incorrectly.

Explanation:

A = base × height

= (7⅖)(2)

= (37/5)(2)

= 74/5

= 14.8 m²

Answer 2

She used the incorrect area formula.

She converted the mixed number to an improper fraction incorrectly.

She multiplied incorrectly.

Explanation:

The area of a parallelogram is

A = bh not A = 1/2 bh

She started with the wrong formula

A = 7 2/5 * 2

Change to an improper fraction

The improper fraction is 37/5 not 35/5

A = 37/5 *2

She multiplied incorrectly

A = 74/5