Question

Giovanna used the calculations below to determine the height of a stack of 7 books that are each 2 and StartFraction 5 over 8 EndFraction inches thick. What was her error? 7 (2 and StartFraction 5 over 8 EndFraction). 7 (2 + StartFraction 5 over 8 EndFraction). 14 + StartFraction 5 over 8 EndFraction. 14 and StartFraction 5 over 8 EndFraction The fraction was not simplified in the last step. Seven was not multiplied by StartFraction 5 over 8 EndFraction. There should be a subtraction step, not an addition step. Two should have been multiplied by StartFraction 5 over 8 EndFraction.

Answer 1

She didn't do the multiplication of 7 times the fraction 5/8 by using distributive property.

so the correct answer is the one that looks like:

Seven was not multiplied by StartFraction 5 over 8 EndFraction.

in your list of options.

Explanation:

If one has a stack of seven books each
`2(5)/(8) \,\,in` thick, one should first convert the mixed number to an addition of an integer plus a fraction

`2(5)/(8) =(2+(5)/(8))`

as she did, and then multiply 7 by the addition, making sure to use distributive property and multiply both terms:

`7\,\,(2+(5)/(8))=7\,*\,12+7\,*\,(5)/(8)=14+(35)/(8)`

and she didn't do the multiplication of 7 times the fraction 5/8