The water acidity in a pool is considered normal when the average… - Vidyadip

Question

The water acidity in a pool is considered normal when the average pH reading of three daily measurements is between 7.2 and 7.8. If the first two pH reading are 7.48 and 7.85, find the range of pH value for the third reading that will result in the acidity level being normal.

✓

Answer

Let the pH value of third reading be x.

$\therefore7.2<\frac{7.48+7.85+\text{x}}{3}<7.8$

⇒ 21.6 < 7.48 + 7.85 + x < 23.4

⇒ 21.6 < 15.33 + x < 23.4

⇒ 21.6 - 15.33 < x < 23.4 - 15.33

⇒ 6.27 < x < 8.07

$\therefore$ The range of pH value for the third reading is lies between 6.27 and 8.07.

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