Same answer as the first one above
The two different isotopes have weights :
w1 = 78.918 amu
w2 = 80.916 amu
average weight w3 = 79.903 amu
The mixing of two components can be modeled as
let the fraction of w1 be 'x'
hence 
now this is a linear equation in 'x'. Substituting the values we get
x = 0.507
hence the percentage of Br79 = 50.7% and the percentage of BR81 = 49.3%
It can help with measurements and when you want to add measurements to a cylinder or a beaker so ya
Answer:
Opposite sides are congruent (AB = DC).
Opposite angels are congruent (D = B).
Consecutive angles are supplementary (A + D = 180°).
If one angle is right, then all angles are right.
The diagonals of a parallelogram bisect each other.
Each diagonal of a parallelogram separates it into two congruent triangles.
Explanation: #if you need any queshtions answered within secs/mins hit me up and I gotchu.
Answer:
A physical matter
Explanation:
A kind of matter with uniform physical properties