Algebra · real student question

Solve 16000000 x 11.0006 + 0.13x = x.

Question

Solve 1600000011.0006+0.13x=x16000000 \cdot 11.0006 + 0.13x = x for xx.

Step-by-step solution

  1. Collapse the constant product first. The left-hand side hides a plain multiplication: 16,000,00011.0006=176,009,60016{,}000{,}000 \cdot 11.0006 = 176{,}009{,}600. Doing this before touching the xx keeps the equation readable: 176,009,600+0.13x=x.176{,}009{,}600 + 0.13x = x.

  2. Recognise the shape of the problem. The unknown appears on both sides, so this is a gross-up: some fixed amount plus 13%13\% of the total equals the total. The standard move is to collect all xx terms on one side.

  3. Subtract 0.13x from both sides. 176,009,600=x0.13x=(10.13)x=0.87x.176{,}009{,}600 = x - 0.13x = (1-0.13)x = 0.87x. Factoring xx out is the key step - 10.13=0.871 - 0.13 = 0.87 is the fraction of the total that the fixed amount represents.

  4. Divide by 0.87. x=176,009,6000.87=17,600,960,00087202,309,885.06.x = \frac{176{,}009{,}600}{0.87} = \frac{17{,}600{,}960{,}000}{87} \approx 202{,}309{,}885.06. The exact value is the fraction 1760096000087\tfrac{17600960000}{87}, which does not terminate, so round only at the end.

  5. Check the answer by substitution. 0.13×202,309,885.0626,300,285.060.13 \times 202{,}309{,}885.06 \approx 26{,}300{,}285.06, and 176,009,600+26,300,285.06202,309,885.06176{,}009{,}600 + 26{,}300{,}285.06 \approx 202{,}309{,}885.06 - the two sides agree.

  6. Note the scaling shortcut. Because the equation is linear and homogeneous in the constant, scaling the constant scales xx by the same factor: the same equation with 160011.0006100=176.0096\tfrac{1600\cdot 11.0006}{100} = 176.0096 gives x202.31x \approx 202.31, exactly one millionth of this answer.

Answer

x=1760096000.87=1760096000087202,309,885.06x = \frac{176009600}{0.87} = \frac{17600960000}{87} \approx 202{,}309{,}885.06

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