# Three balls

Three balls $$A, B, C$$ of respective masses $$5\text{ kg}, 5 \text{ kg}, 20 \text{ kg}$$ stand in a row in that order.

Now, ball $$A$$ moves towards $$B$$ at speed $$1\text{ m/s}$$ while $$B$$ and $$C$$ are still at rest. There aren't any frictional forces, and the collision between balls $$A$$ and $$B$$ are perfectly elastic.

If the final velocity of ball $$C$$ is $$0.4\text{ m/s},$$ what will be the final speed $$($$in $$\text{m/s})$$ of ball $$A,$$ to 1 decimal place?

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