Testing the multiplication for each case, it is found that she should round the square root of 2 to three decimal digits.
The square root of 2 is given by:
[tex]\sqrt{2} = 1.41421356237[/tex]
With one decimal digit, the result of the multiplication is:
[tex]5 \times \sqrt{2} = 5 \times 1.4 = 7 < 7.05[/tex]
With two decimal digits, the result of the multiplication is:
[tex]5 \times \sqrt{2} = 5 \times 1.41 = 7.05 = 7.05[/tex]
With three decimal digits, the result of the multiplication is:
[tex]5 \times \sqrt{2} = 5 \times 1.414 = 7.07 > 7.05[/tex]
Hence, she should round the square root of 2 to three decimal digits.
You can learn more about rounding at https://brainly.com/question/17248958