In the

In the 6th class, the average half-year mark in physics was 1.7. At the end of the year, Maťo improved his mark from 2 to 1, Ivanka from 3 to 2, and Elenka from 4 to 2. Pavlík worsened his mark from 3 to 4. The average mark of the whole class thus improved by 0.1. How many children in this class could have a physics mark one (the best) at the end of the year maximally?

Correct answer:

n =  30
a =  12

Step-by-step explanation:

$$\begin{gathered} p_2\cdot n=a\cdot 1+(n-a)\cdot 2 \\ 1.6\cdot 30=a\cdot 1+(30-a)\cdot 2 \\ a=12 \end{gathered}$$

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