Subtracting mixed fractions.

[Guest]

15 1/4 minus 9 9/10.
Show work and explain borrowing.

[Guest]

Deal with the whole numbers and the fractions separately

15 - 9 = 6

So re-write the sum as 6 + (1/4 - 9/10)

Get LCM of Denominators..... 20 .....change the fractions to 20ths..

6 + (5/20 - 18/20) ..cannot subtract as normal...it leaves -ve part..

6 + ( - 13/20)....which is OK....this equals 5 7/20 as a mixed number all in one step..

But to explain it by borrowing......

Same as 5 + (1 - 13/20).....this is borrowing 1 whole

Same as 5 + (20/20 - 13/20) .....split 1 whole in to 20ths and subtract as normal

Same as 5 + ( 7/20)

written as a mixed number 5 7/20.

OR do this way.....

6 + (5/20 - 18/20) ..cannot subtract as normal ...leaves -ve part..

5 + ( 1 + 5/20 - 18/20) this is borrowing 1 whole..


5 + ( 20/20 + 5/20 - 18/20) change to 20ths and add together


5 + ( 25/20 - 18/20)


5 + ( 7/20 )

written as a mixed number 5 7/20.

[Guest]

First convert mixed fractions into improper fractions i.e.
15 1/4 =61/4 and
9 9/10 =99/10 now
61/4-99/10
L.C.M.of 4 and 10 is 20
(305-198)/20=107/20
Answer :5 7/20

[Guest]

When we are dealing with mathematical calculations and end up with improper fractions at the end, normally we change the improper fractions to mixed numbers to "simplify" and make reading more easily understood......So you end up with a number of whole things plus a fraction of a whole.

So why would you then change an addition or subtraction mixed number problem to improper fractions.? ?

When you do it makes the numbers in the calculation much larger during the calculations and then you change the answer back to a mixed number again at the end. ? ?

Imagine the size of numbers you would have had if the fractions had been hundredths of thousandths.....

You normally have to change mixed numbers to improper fractions to to do multiplying of division but not necessary for addition or subtractions.