6. (15 points) The radar received the signal reflected from the target after 15 microseconds. Determine the distance to the target, given that the speed of the radar signal is $300000 \mathrm{kM} / \mathrm{c}$. Note that one microsecond is one millionth of a second.
Answer: 2250 m

Solution. In 15 microseconds, the signal travels the distance from the radar to the target and back. Therefore, the distance to the target is:

$$
S=v \frac{t}{2}=3 \cdot 10^{8} \cdot \frac{15 \cdot 10^{-6}}{2}=2250 \mathrm{~m}
$$

## Preliminary Stage

7th grade

## Variant 2

## Problems, answers, and evaluation criteria