Approximation Math Example 1

Follow the full solution, then compare it with the other examples linked below.

Example 1

easy
Estimate 50\sqrt{50} to one decimal place without a calculator.

Solution

  1. 1
    Identify perfect squares on either side: 72=497^2 = 49 and 82=648^2 = 64. So 7<50<87 < \sqrt{50} < 8.
  2. 2
    50\sqrt{50} is very close to 49=7\sqrt{49} = 7. The gap between 4949 and 6464 is 1515; 5050 is 11 above 4949, so 50โ‰ˆ7+115โ‰ˆ7.07\sqrt{50} \approx 7 + \dfrac{1}{15} \approx 7.07.
  3. 3
    To one decimal place: 50โ‰ˆ7.1\sqrt{50} \approx 7.1.

Answer

50โ‰ˆ7.1\sqrt{50} \approx 7.1
Linear interpolation between known square roots gives a reasonable first approximation. Knowing the perfect squares on either side of the target immediately brackets the root, and the fraction of the gap gives the tenths digit.

About Approximation

A value intentionally chosen to be close to but not exactly equal to the true value, with a known or estimated error.

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