On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?

The nearest star would be approximately 4064km away from the sun.

Explanation:

The distance between the sun and the earth (in real life) is 147.36 * 10^6 km i. e. 1.4736 * 10^11m. In the analogy, we're told the distance from the earth to the grapefruit sized sun is only 15m. Hence, if we're to find a ratio of the real distance to the analogical distance, it would be given as

Real distance : Analogical distance

= 1.4736*10^11 : 15

= 9.824*10^9 : 1

This means that 1m in the analogical scale is equivalent to 9.824*10^9m in reality.

The nearest stars to the sun are about 4.22 light-years from the earth. In meters, that is

4.22 light-years * 9.461 * 10^15

= 3.9924 * 10^16m

Note: 1 light-year = 9.461 * 10^15m

Using the analogical scale, the nearest star would then be

(3.9924 * 10^16) / (9.824 * 10^9) = 4063925.08m = 4063.925km

Therefore, if the sun was the size of a grapefruit, the nearest star would be approximately 4064km away from the sun.