# The water acidity in a pool is considered normal

Question:

The water acidity in a pool is considered normal when the average pH reading of three daily measurements is between 8.2 and 8.5. If the first two pH readings are 8.48 and 8.35, find the range of pH value for the third reading that will result in the acidity level being normal.

Solution:

According to the question,

Now, let the third reading be ‘x’

Average pH should be between 8.2 and 8.5

Average pH = (8.48 + 8.35 + x)/3

$\Rightarrow 8.2<\frac{8.48+8.35+x}{3}<8.5$

Multiplying each term by 3, we get

⇒ 24.6 < 16.83 + x < 25.5

Subtracting 16.83 from each term, we get

⇒ 7.77 < x < 8.67

Therefore, from the above equation,

We get that,

The third pH reading should be between 7.77 and 8.67