Answer:
39.7 m
Explanation:
First, we conside only the last second of fall of the body. We can apply the following suvat equation:

where, taking downward as positive direction:
s = 23 m is the displacement of the body
t = 1 s is the time interval considered
is the acceleration
u is the velocity of the body at the beginning of that second
Solving for u, we find:

Now we can call this velocity that we found v,
v = 18 m/s
And we can now consider the first part of the fall, where we can apply the following suvat equation:

where
v = 18 m/s
u = 0 (the body falls from rest)
s' is the displacement of the body before the last second
Solving for s',

Therefore, the total heigth of the building is the sum of s and s':
h = s + s' = 23 m + 16.7 m = 39.7 m
Answer:
3MgCl2 has 9 atoms.
Explanation:
The Element Magnesium (Mg) has 3 atoms.
The Element Chloride (Cl) has 6 attoms.
Their fore 6 + 3 is 9 of course. 3MgCl2 has 9 atoms.
BTW: 3MgCl2 is a molecular compound as well as H2O and CO2.