Source: Extra Practice

A physical quantity XX is given by X=A2B3CDX = \frac{A^2 B^3}{C \sqrt{D}}. If the percentage errors in the measurements of A,B,C,A, B, C, and DD are 1%,2%,3%1\%, 2\%, 3\%, and 4%4\% respectively, what is the total percentage error in XX?

Options

Option A is correct

13%13\%

Option B

14%14\%

Option C

15%15\%

Option D

16%16\%

Explanation

For a quantity X=ApBqCrDsX = \frac{A^p B^q}{C^r D^s}, the maximum percentage error in XX is given by: %EX=p(%EA)+q(%EB)+r(%EC)+s(%ED)\%E_X = p(\%E_A) + q(\%E_B) + r(\%E_C) + s(\%E_D)

In the given equation, X=A2B3C1D1/2X = A^2 B^3 C^{-1} D^{-1/2}. Note that the powers are always taken as positive when summing errors. %EX=2(%EA)+3(%EB)+1(%EC)+12(%ED)\%E_X = 2(\%E_A) + 3(\%E_B) + 1(\%E_C) + \frac{1}{2}(\%E_D)

Given percentage errors:

  • %EA=1%\%E_A = 1\%
  • %EB=2%\%E_B = 2\%
  • %EC=3%\%E_C = 3\%
  • %ED=4%\%E_D = 4\%

Substitute these values into the formula: %EX=2(1%)+3(2%)+1(3%)+12(4%)\%E_X = 2(1\%) + 3(2\%) + 1(3\%) + \frac{1}{2}(4\%) %EX=2%+6%+3%+2%\%E_X = 2\% + 6\% + 3\% + 2\% %EX=13%\%E_X = 13\%