Anonymous
Anonymous asked in Education & ReferenceHomework Help · 1 decade ago

help with multiplying fractions?

1/4*1/2

3/4*8/9

15*2/3

2 1/3*3 1/2

4 2/5*3

5 5/6*2 4/5

estimate 9 5/6 divided by 2 1/8 is it 4 1/2 or 5

6 divided by 1/2 ?

13 Answers

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  • 1 decade ago
    Favorite Answer

    Multiply all the numerators, multiply all the denominators.

    For example 3/4*8/9 = 24/36

    Simplify if you can (common factors in the numerator and denominator can be cancelled.

    In the example above, the numerator and denominator have a common factor of 12. So you can divide each by 12 and cancel, leaving you with a simplified answer of 2/3.

    If you have a proper fraction like 2 1/3 and 3 1/2, first you have to convert these to improper fractions.

    2 1/3 = 7/3 3 1/2 = 7/2

    Then multiply as I described above.

    When you divide by a fraction, you multiply by the reciprocal, so

    9 5/6 divided by 2 1/8 is 59/6 divided by 17/8 which is the same as

    59/6 * 8/17.

    I hope that helps.

  • 6 years ago

    All you have to do is multiply across the top and bottom

    For example 2/5 x 3/4 equals 6/20 because 2 x 3= 6 and 5x4=20 so that equals six twentieths

    If you are doing Mixed numbers 1 and 1/5 you turn into a improper Fraction with would be 6/5 because 5 x 1 +1 in other words denominator times whole number plus numerator. Then multiply the two fractions.

    I hope this helps

  • 1 decade ago

    You have types of problems here. I will help you with one of each.

    3/4*1/2

    Put this into two multiplication problems first:

    3*1 and 4*2; denominator and numerator

    this gives you 3/8 IE; 3*1 over 4*2

    therefor 3/4*1/2=3/8

    this is the same type problem with the addition of whole numbers, no problem, tackle the whole numbers first and repeat the proceedure used in the first problem to wit;

    5 5/6 * 2 4/5

    this actually can be read as (5/1 + 5/6) *(2/1+4/5)

    Now for some common sense, how many 6ths are there in 1? Obviously there are 6. So,,,,how many 6ths in 5?

    How anout 6*5 or 30? Same widea with the second part 5*2=10 so,,, we now have (30/6+5/6)*(10/5+4/5)

    35/6 * 14/5

    (35*14)/(6*5) 490/30

    Divide 490/30=16.333333 leave it at 16 as a whole number and leave the remainder at 10/30 or 16 10/30 or

    16 1/3

    The second type is the last one 6 divided by 1\2

    lay this out as 6/1 / 1/2. This one will look a bit funny but it actually is done the same as before with one odd twist.

    "It's exactly the same only different" OK so I'm not funny!!

    flip ONE of the elements over making them agreeable. Flip the 1/2 over and notice the agreement: 6/1 and 2/1.

    We also flip the process from division to multiplication.

    IE: 6/1 * 2/1= 12/1 + 12

    I went all around the bush with this so you could feel the math. Science, math etc MUST be felt or you will never master it.

  • Anonymous
    1 decade ago

    Just multiply the tops across and then multiply the bottoms across.

    1/4 x 1/2 = 1/8

    3/4 x 8/9 = 24/36 (simplifiy) = 2/3

    You can put 15 over 1, and it has the same value.

    15/1 x 2/3 = 30/3 (simplify) = 10

    Now, for mixed numbers, you have to change them to fractions. Multiply the denominator times the whole number plus the numerator and put the answer over the denominator. Like this:

    2 1/3

    3 x 2 + 1 =7

    2 1/3 = 7/3

    3 1/2

    2 x 3 + 1 = 7

    3 1/2 = 7/2

    7/3 x 7/2 = 49/6

    ----------------------

    4 2/5

    5 x 4 + 2 = 22

    4 2/5 = 22/5

    22/5 x 3/1 = 66/5

    -----------------------

    5 5/6

    6 x 5 +5 = 35

    5 5/6 = 35/6

    2 4/5

    5 x 2 + 4 = 14

    2 4/5 = 14/5

    35/6 x 14/5 = 490/30 (simplify) = 98/6 = 49/3

    -----------------------------------------------------------

    Okay, when you divide fractions, you flip the second fraction and multiply.

    9 5/6

    6 x 9 + 5 = 59

    9 5/6 = 59/6

    2 1/8

    8 x 2 + 1 = 17

    2 1/8 = 17/8

    59/6 / 17/8

    59/6 x 8/17 = 472/102 (simplify) = 236/51= 4.627 ~ 4.5

    -------------------------------------------------------------------------

    6 / 1/2

    6/1 x 2/1 = 12/1 = 12

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  • 1 decade ago

    1/4 X 1/2 = 1/8

    this is because 4 x 2 is 8 and 1 x 1 is 1!

    now that you know that, do the second problem the same way.

    for 15 x 2/3, you have to do 15/1 x 2/3 and then do it the same way. so 15 x 2 is 30 and 1 x 3 is 3 so 30/3 is 10. that's the answer to the third problem.

    to simplify a number like 2 1/3 into fraction form, you multiply 2 by 3 (6) and add 1 (7). so you'll have 7/3 as your first fraction for problem number 4. now simplify the second one the same way and multiply them together like you did for the previous problems.

    the same goes for problems number four and five.

    as for problem number 6, use a calculator! :)

  • 1 decade ago

    When multiplying fractions, you don't worry if the denominator is the same or not, just multiply the top and then the bottom. For example...

    1/4 *1/2 = 1 times 1 is 1 and 4 times 2 is 8 so the answer is 1/8. This is already lowest terms, so you are done.

    When multiplying mixed numbers, change them to fractions first... like 2 1/3 = 7/3... then multiply as mentioned above...

    On whole numbers, like 15... just stick a one under it to make a denominator..15/1, and then mulitiply... you can do this and good luck!

  • 1 decade ago

    First, if they're compound numbers (a whole number and a fraction) convert it into a fraction. For example, 1 2/3 = 5/3.

    Now, to multiply the fractions, multiply the two top numbers and multiply the two bottom numbers. For example 5/3 x 7/4 = 35/12.

    Finally, simplify the resulting fraction. For example, 35/12 = 2 11/12.

    That's it!

    To divide fractions, first convert compound numbers into fractions, (if necessary), then multiply the top number of the first fraction by the bottom number of the fraction its being divided by.

    Place the result at the top of the answer fraction.

    Now, multiply the bottom number of the first fraction by the top number of the fraction its being divided by.

    Place the result at the bottom of the answer fraction.

    Simplify the resulting fraction.

    For example: 3/4 divided by 5/6 = 18/20 = 9/10

    That's it!

  • 1 decade ago

    do this:

    use the first two numbers of the fraction and multiply them. In this case, it would be 1 * 1 which equals 1. That is the first part of the answer. Then multiply the second numbers in the fractions together, in this case it would be 4 and 2, which would equal 8. your answer is 1/8.

    1/4 * 1/2

    Do that for the rest of the problems. Simplify if nessicary.

  • 1 decade ago

    ok for division you make the mixed number into an improper fraction (formula: denominator times whole number + numerator over denominator): 9 5/6= (59/6) and 2 1/8=(17/8)

    then you switch the top and bottom numbers (numerator and denominator) in the second fraction:

    (17/8)= 8/17

    so your final equation:

    (59/6) times (8/17)

  • 1 decade ago

    multiplying fractions- multiply the neumerators and the denominators

    ex: 3/4*1/2=3/8

    dividing fractions- write down the first fraction, change the division sign to a multiplication sign, flip the second fraction, multiply

    Source(s): my math teachers
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