Answer: 0.9.

Solution: After the first minute, $\frac{1}{2}$ of the initial feed remains, after the second minute, $\frac{1}{2} \cdot \frac{2}{3}$, and so on. After the 9th minute, $\frac{1}{2} \cdot \frac{2}{3} \cdots \cdots \frac{9}{10} = \frac{1}{10}$ of the initial amount of feed remains, i.e., 0.9 grams.

## Variant 2

Dasha poured 8 grams of feed into the aquarium for the fish. In the first minute, they ate half of the feed, in the second minute, a third of the remaining feed, in the third minute, a quarter of the remaining feed, and so on, in the ninth minute, a tenth of the remaining feed. How many grams of feed are left floating in the aquarium?

Answer: 0.8.

## Variant 3

Dasha poured 7 grams of feed into the aquarium for the fish. In the first minute, they ate half of the feed, in the second minute, a third of the remaining feed, in the third minute, a quarter of the remaining feed, and so on, in the ninth minute, a tenth of the remaining feed. How many grams of feed are left floating in the aquarium?

Answer: 0.7.

## Variant 4

Dasha poured 6 grams of feed into the aquarium for the fish. In the first minute, they ate half of the feed, in the second minute, a third of the remaining feed, in the third minute, a quarter of the remaining feed, and so on, in the ninth minute, a tenth of the remaining feed. How many grams of feed are left floating in the aquarium?

Answer: 0.6.

## Variant 5

Dasha poured 5 grams of feed into the aquarium for the fish. In the first minute, they ate half of the feed, in the second minute, a third of the remaining feed, in the third minute, a quarter of the remaining feed, and so on, in the ninth minute, a tenth of the remaining feed. How many grams of feed are left floating in the aquarium?

Answer: 0.5.
# 6. Option 1

Dasha poured 9 grams of feed into the aquarium for the fish. In the first minute, they ate half of the feed, in the second minute - a third of the remaining feed, in the third minute - a quarter of the remaining feed, and so on, in the ninth minute - a tenth of the remaining feed. How many grams of feed are left floating in the aquarium?