The average height

The average height of six friends is 181 cm. Peter came among them, which reduced the average height by 2 cm. Calculate the Peter's height.

Correct result:

x =  167 cm

Solution:

$$\begin{gathered} (181\cdot 6+x)\mathrm{/}(6+1)=181-2 \\ 0.142857x=23.857143 \\ x=167=167\text{ cm} \end{gathered}$$

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