$3+$ [Examples and counterexamples. Constructions]

In the zoo, there are 10 elephants and huge pan scales. It is known that if any four elephants stand on the left pan, and any three on the right, the left pan will outweigh. Five elephants stood on the left pan and four on the right. Will the left pan definitely outweigh?
Counterexample. Let five elephants weigh 7 tons each, and another five weigh 9 tons each. Then any four elephants on the left pan of the scales together weigh no less than $4 \cdot 7=28$ tons, while any three elephants on the right pan weigh no more than $3 \cdot 9=27$ tons, and the left pan will indeed outweigh.

But if the five "light" elephants with a total mass of $5 \cdot 7=35$ tons stand on the left pan, and four "heavy" elephants with a total mass of $4 \cdot 9=36$ tons on the right, then the right pan will outweigh.

## Answer

Not necessarily.