# AStronomy/ Math

I do not understand how to do one of my online homework questions:

What is the Schwarzschild radius of a 100 million-solar-mass black hole? The mass of the Sun is about 2 × 1030 kg, and the formula for the Schwarzschild radius of a black hole of mass M is:
R=2GMc2,
where G=6.67×10−11m2kg×s2; c=3×108m/s.

The choices are:

300 million km
3 million km
3,000 km
3 km
30 km

1. 👍 0
2. 👎 0
3. 👁 105
1. just plug in the figures:

R = 2GM/c^2
= (2)(6.67*10^-11)(100*10^6*2*10^30) / (9*10^16)
= 3*10^11 m
= 3*10^8 km
= 3*10^2 million km
= 300 million km

1. 👍 0
2. 👎 0
posted by Steve
2. Thank you

1. 👍 0
2. 👎 0
posted by Kaitlyn
3. 300 million km

1. 👍 0
2. 👎 0
posted by kat

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