Cross Multiply
Cross Multiply
If two fractions are equal, say
then it is always true that the products of the numbers given by
are also equal, or ad←= bc. This is the most common form of cross multiplication. That
implies ad = bc can be shown by multiplying both sides of
by the common denominator bd and canceling.
Cross multiplying is a common first step in solving proportions:
is equivalent to
3 × 21 = x × 7 or 7x = 63
Therefore, x = 9.
Adding fractions can also be done with cross multiplication.
The cross product of two vectors does not involve cross multiplying; the resemblance between the two terms is accidental.
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Cross Multiply