Arithmetically 83012

There were 21 pupils in the class, and arithmetically, the average height of these pupils was 163 cm. Calculate what the average height in the class will be if:

a) A 159 cm tall student was added to the class
b) A 169 cm tall student left the class

Correct answer:

a =  162.8182 cm
b =  162.7 cm

Step-by-step explanation:

$$\begin{gathered} n=21 \\ p=163\text{cm} \\ x=159\text{cm} \\ a=\frac{n\cdot p+x}{n+1}=\frac{21\cdot 163+159}{21+1}=162.8182\text{cm} \end{gathered}$$

$$\begin{gathered} y=169\text{cm} \\ b=\frac{n\cdot p-y}{n-1}=\frac{21\cdot 163-169}{21-1}=162.7\text{cm} \end{gathered}$$

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