Lowest Common Demoninator

Why bother with LCD’s? Rescaling.

Rescaling is used to get number to the same unit.

ex) 1/8 + 3/4 = 1/8 + (3/4 * 2/2) = 1/8 + 6/8 = 1+6/8 = 7/8

Note: You dont need to rescale for multiplication or division.

Rule: a/b = a*k/b*k as long as k!=0,b!=0

Addition of Subtraction:

1) Rescale both

ex) a/b ± c/d
(a/b * b/d) ± (c/d * d/b)
ad/bd ± cb/db
ad±cb/bd

ex)
7/15 + 3/10
(7/15 * 2/2) + (3/10 * 3/3)
14/30 + 9/30 = 23/30

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