Algebra · real student question

Solve the equation (5399 - x) / x = 4.8116 for x.

Question

Solve for xx:

5399xx=4.8116\frac{5399-x}{x}=4.8116

Step-by-step solution

  1. Interpret the ratio. The equation states that the part removed from 53995399 is 4.81164.8116 times as large as xx itself. So 53995399 is being split into xx plus 4.8116x4.8116x, and xx should come out roughly one sixth of the total — a useful sanity target before computing.

  2. Multiply through by xx. Any solution has x0x\neq 0, so

    5399x=4.8116x5399-x=4.8116x

  3. Add xx to both sides.

    5399=4.8116x+x=5.8116x5399=4.8116x+x=5.8116x

    The 11 comes from the x-x that was sitting in the numerator; dropping it would give 1122.21122.2, badly wrong.

  4. Divide.

    x=53995.8116=929.00406929.00x=\frac{5399}{5.8116}=929.00406\ldots\approx 929.00

    Rounded to two decimals the trailing digits are 0000, so quoting 929.03929.03 overshoots by three hundredths.

  5. Check the split. The leftover is 5399929.00406=4469.995945399-929.00406=4469.99594, and

    4469.99594929.00406=4.81160\frac{4469.99594}{929.00406}=4.81160

    matching the given ratio to five significant figures, and 929.00+4470.00=5399.00929.00+4470.00=5399.00 recovers the total.

Answer

x=53995.8116929.00x=\frac{5399}{5.8116}\approx 929.00

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