Question:medium

A quantity $ Q $ is formulated as $ Q = X^{-2} Y^{3/2} Z^{-2/5} $. $ X $, $ Y $, and $ Z $ are independent parameters which have fractional errors of 0.1, 0.2, and 0.5, respectively in measurement. The maximum fractional error of $ Q $ is:

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When dealing with propagation of errors, remember to apply the error propagation formula, which involves the sum of the products of the partial derivatives and the corresponding fractional errors of each variable.
Updated On: Jan 14, 2026
  • 0.7
  • 0.1
  • 0.8
  • 0.6
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The Correct Option is A

Solution and Explanation

The maximum fractional error in the quantity \(Q\) is determined by propagating the errors from parameters \(X\), \(Y\), and \(Z\) through the equation \(Q = X^{-2} Y^{3/2} Z^{-2/5}\). For a quantity of the form \(Q = X^a Y^b Z^c\), the fractional error is given by \(\frac{\Delta Q}{Q} = |a| \frac{\Delta X}{X} + |b| \frac{\Delta Y}{Y} + |c| \frac{\Delta Z}{Z}\).

For the given function, \(a = -2\), \(b = \frac{3}{2}\), and \(c = -\frac{2}{5}\). The fractional errors are:

  • \(\frac{\Delta X}{X} = 0.1\)
  • \(\frac{\Delta Y}{Y} = 0.2\)
  • \(\frac{\Delta Z}{Z} = 0.5\)

Substituting these values into the fractional error formula:

\(\frac{\Delta Q}{Q} = |-2| \times 0.1 + \left|\frac{3}{2}\right| \times 0.2 + \left|-\frac{2}{5}\right| \times 0.5\)

The individual terms are:

  • \(|-2| \times 0.1 = 0.2\)
  • \(\left|\frac{3}{2}\right| \times 0.2 = 0.3\)
  • \(\left|-\frac{2}{5}\right| \times 0.5 = 0.2\)

Summing these terms yields:

\(\frac{\Delta Q}{Q} = 0.2 + 0.3 + 0.2 = 0.7\)

The maximum fractional error of \(Q\) is 0.7.

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