Propagation error in finding the perimeter and area, .

[megkirch]

Homework Statement

I want to measure the size of my back yard. I estimate that I can measure the length and width of the yard using a tape measure to an accuracy of 0.05m. I find that the length of the yard is 8.6 m and the width is 7 m.



Calculate the perimeter of the yard and its error
Now calculate the area of the yard and its error

Homework Equations

s=square root(changeA)^2+(changeB)^2)

The Attempt at a Solution

I calculated the perimeter and got 31.4m. i can't figure out how to get the error in the perimeter. I thought it would be 8.55(2)+6.95(2) =31.0 -31.4=.4 but its not correct

 

[256bits]

You say your accuracy is 0.05m.

Then the length is 8.60 m. the error in measurement is 0.05m
The width is 7.00m with a measurement error of 0.05m