A scientist estimated that a mixture would need 3 milliliters of a chemical to balance. The actual amount needed was 7 milliliters. What was the percent error of the scientist's estimation?
133.33%
3%
42.86%
57.14%

Question

A scientist estimated that a mixture would need 3 milliliters of a chemical to balance. The actual amount needed was 7 milliliters. What was the percent error of the scientist's estimation?
133.33%
3%
42.86%
57.14%

samara8954 · Answer

@mathstudent55

mokeira · Answer

find the error
(7-3)= error
then change to precentage

mathstudent55 · Answer

$percent ~error = \dfrac{new~value - old~value}{old~value} \times 100\%$

Use old value = 3 and new value = .

samara8954 · Answer

so the precentage is 3

samara8954 · Answer

am I correct

samara8954 · Answer

so now what

mathstudent55 · Answer

Wait. I just reread the question. I made a mistake. 
The formula above is correct. 
You need to use 7 as the old value since 7 is what we are comparing to.
3 is the new value since this is the value whose percent error we want.

$percent ~error = \dfrac{new~value - old~value}{old~value} \times 100\%$

$percent ~error = \dfrac{3 - 7}{7} \times 100\%$

mathstudent55 · Answer

$\dfrac{3 - 7}{7} \times 100\% = \dfrac{-4}{7} \times 100\% = -0.5714 \times 100\%
= -57.14\%$
The error in the estimate is 57.14%.
The negative sign in the formula means the the estimate is 57.14% lower than the correct value.