Algebra · real student question

Solve the equation x - 1 = 0.99x.

Question

Solve

x1=0.99xx-1=0.99x

Step-by-step solution

  1. Get both xx terms on the same side. The variable appears on the left and the right, so nothing can be divided out yet. Subtract 0.99x0.99x from both sides:

    x0.99x1=00.01x1=0x-0.99x-1=0\qquad\Longrightarrow\qquad0.01x-1=0

    The coefficient is 10.99=0.011-0.99=0.01 — a small number, which is precisely why the answer will be large.

  2. Isolate the term in xx. Add 11 to both sides:

    0.01x=10.01x=1

  3. Divide by the coefficient. Dividing by 0.010.01 is the same as multiplying by 100100, since 0.01=11000.01=\tfrac{1}{100}:

    x=10.01=100x=\frac{1}{0.01}=100

    Working in fractions avoids any decimal drift: 1100x=1x=100\tfrac{1}{100}x=1\Rightarrow x=100.

  4. Verify in the original equation. Left side: 1001=99100-1=99. Right side: 0.99×100=990.99\times100=99 ✓. The check was also run in exact rational arithmetic, so the value is 100100 on the nose, not a rounded approximation.

  5. Understand what the equation says. It asks for the number that drops by exactly 11 when reduced by 1%1\% — so 11 must be that 1%1\%, making the whole 100100. Reading the structure this way turns the algebra into a one-line percentage argument, and it also predicts that x1=0.98xx-1=0.98x would give 5050, since then 11 is 2%2\% of the whole.

Answer

x=100x=100

Need to solve a different problem like this? Open the solver →