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1995-07-28
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êêïDIVIDING FRACTIONS, INTERMEDIATE LEVEL
è In this section we will be looking at dividing positive and/or
negative fractions.ïYou recall in the Elementary Level that when you
divided two positive fractions, you always got a positive fraction
as an answer.ïIn this section we are really considering dividing
any fraction, positive or negative, by any other fraction, positive
or negative.ïThere will be two rules to cover the different cases.
The first rule is used when dividing two fractions that are both
positive or both negative.ïThe second rule will be for dividing two
fractions with different signs.ïThe following list shows the set of
all fractions.
êêêêïFractions
#êë ... -╩ï-╔è╚è╔è╩è╦è╠è═è╬ ...
êêè 1è1è1è1è1è1è1è1è1
#êë ... -╩ï-╔è╚è╔è╩è╦è╠è═è╬ ...
êêè 2è2è2è2è2è2è2è2è2
#êë ... -╦ï-╔è╚è╔è╩è╦è╠è═è╬ ...
êêè 3è3è3è3è3è3è3è3è3
êêêê.
êêêê.
êêêê.
Rule 6)ïTo divide two fractions that are both positive,ïyou should
divide them like we did in the Elementary Level.ïTo divide two
fractions that are both negative, you should change the operation to
multiplication and invert the second fraction like we did in the
Elementary Level.ïThen you should multiply the two numerators and the
two denominators remembering that the product or quotient of two nega-
tive numbers is positive.ïThen, cancel like factors and simplify.
Examples
ï1) Both fractions positive.
ï5è 9ê 5è15ê5∙15êï5∙3∙5êè 25êè25
# ── ÷ ──è=è── ∙ ──è=è────è=è─────────è=è───────è=è──
12è15ê12è 9ê12∙9ê2∙2∙3∙3∙3ê2∙2∙3∙3ê36
2) Both fractions negative.
è -2è-3ë -2è8ê -2∙8ê -2∙2∙2∙2ê-16ê16
#è ── ÷ ──è=ï── ∙ ─è=è──────è=è────────è=è───è=è──
ë9è 8ê9ï-3ê9∙(-3)ê3∙3∙(-3)ê-27ê27
Rule 7)ïTo divide two fractions that have different signs, you should
change the operation to multiplication and invert the second fraction.
Then, you should multiply the two numerators and the two denominators
remembering that the product or quotient of a positive number and a
negative number is negative.
3) One fraction positive and the second fraction negative.
êè2è10ê2è-3ê2∙(-3)ê2∙(-3)ê-3
#êè─ ÷ ──è=è─ ∙ ──è=è──────è=è──────è=è──
êè7è-3ê7è10ê 7∙10êï7∙2∙5ê35
4) The first fraction negative and the second fraction positive.
ê -1è 5ê-1è12ê-1∙12ê-1∙2∙2∙3ê-3
#ê ── ÷ ──è=è── ∙ ──è=è─────è=è────────è=è──
êï4è12ê 4è 5ê 4∙5êè2∙2∙5êï5