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Divide Rational
Numbers
Honors Math – Grade 7
A research vessel lowers a submersible 49.2 m below sea
level at a descent rate of 4.1 m per second. In how many
seconds will the submersible reach the targeted depth?
What are the important facts?
Express the numbers as rational numbers.
What operation does the problem suggest?
KEY CONCEPT
Divide Two Rational Numbers
To multiply rational numbers:
1. If the dividend and divisor have like signs, the quotient is positive!
2. If the dividend and divisor have unlike signs, the quotient is negative!
Remember to first divide the rational numbers and then determine the sign
 49.2  (4.1)
3  (0.075)
To divide with decimals, remember to
move the decimal point in the
divisor– changing it to a whole
number—and then move the
decimal point in the dividend the
same number of times.
3  18 
  
5  25 
 3 1
   
 4 2
Remember, when dividing two
fractions, to multiply by the
reciprocal of the divisor.
Also, all quotients must be expressed in
simplest form!
1  1
 12   4 
2  2
1  5
2  
2  6
Remember when dividing mixed
numbers, to change the mixed
numbers to improper fractions and
then multiply by the reciprocal.
A Complex Fraction has a fraction as
a term in the numerator or
denominator or both.
Simplify by dividing!
 80
1
3
3
 0.0168
 5 .6