Algebra · real student question

Solve the equation (9127 - x) / x = 0.934 for x.

Question

Solve for xx:

9127xx=0.934\frac{9127-x}{x}=0.934

Step-by-step solution

  1. Read what the ratio means. The numerator is the part of 91279127 left after removing xx, so the equation says the leftover is 0.9340.934 times xx. Since 0.9340.934 is just under 11, the two parts are nearly equal and xx should come out slightly above half of 91279127, i.e. a little over 45634563.

  2. Clear the denominator. A solution must have x0x\neq 0, so multiplying by xx is safe:

    9127x=0.934x9127-x=0.934x

  3. Collect the xx terms. Adding xx to both sides:

    9127=0.934x+x=1.934x9127=0.934x+x=1.934x

    The coefficient is 1.9341.934, not 0.9340.934 — the extra 11 comes from the x-x that was in the numerator.

  4. Divide.

    x=91271.934=4719.23474719.23x=\frac{9127}{1.934}=4719.2347\ldots\approx 4719.23

    Exactly, x=91270001934=4563500967x=\frac{9127000}{1934}=\frac{4563500}{967}, which does not reduce further (967967 is prime).

  5. Substitute back to four decimals. The leftover is 91274719.2347=4407.76539127-4719.2347=4407.7653, and

    4407.76534719.2347=0.93400\frac{4407.7653}{4719.2347}=0.93400

    exactly as required. By contrast 4719.754719.75 gives 0.933790.93379, which misses the target ratio, so it is not the solution.

Answer

x=91271.9344719.23x=\frac{9127}{1.934}\approx 4719.23

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