Dinosaurs

More than 30 and less than 60 dinosaurs have met at the pond. A quarter of them bathed and 1/7 saws and the rest gripped. How many were at the pond? How many were there?

Correct result:

n =  56
j =  8

Solution:

$$\begin{gathered} n_1=4\cdot 7=28 \\ 30<n<60 \\ n=2\cdot n_1=2\cdot 28=56 \end{gathered}$$

$j=n\mathrm{/}7=56\mathrm{/}7=8$

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