How do you find the GCD?

Question

I'm subtraction fractions, which i havent done in a while. There's fractions with different demonoators, and fractions subtractioning whole numbers. any help? here are the fractions

7/10ths - 3/5ths

7 and 5/9ths - 4



how do you change the fraction? any answers

Answer 1

its not GCD its LCD lowest common denominator
multiply 3 fifths by 2 over 2 to get 6 tenths 7 tenths minus 6 tenths = 1 tenth

denominator times whole number plus numerator makes an improper fraction in ur case 68 ninths minus 4 over 1 multiply 4 over 1 by nine to get 68 ninths minus 36 ninths= 32 ninths

Answer 2

You have to make the denominators (numbers on the bottom) the same.
For example:
7/10 3/5
the denominators are 10 and 5
you could do it like this:
since 10/5 =2, 5x2=10
therefore, this fraction must be multiplied by 2 to be used in this equation
3x2 = 6
5x2=10
and your fraction is 6/10
7/10-6/10=1/10

For the next one, make the whole number part of the fraction too.
7 5/9 = 9x7 whole nines + 5
=68/9
4 whole parts or 4x9
=36/9
Then, 68/9 - 36/9 = 32/9

Answer 3

for the 7/10-3/5 problem u change 3/5 to 6/10 so now ur problem is 7/10-6/10 which the answer is 1/10.

for the 7 and 5/9-4 problem u change 4 to 4/1 then u change 7 and 5/9 to 68/9 so u subtract 68/9-4/1 but ur not done yet u have to leave 68/9 the same but u change 4/1 to 36/9 so then u just subtract 68/9-36/9 to get 32/9 which simplifies to 3 and 5/9.

(P.S.- i am only in 6th grade)

Answer 4

the previous answers are great! but remember the place value when doing simple arithmetic. for example, there is no need to convert the 7 and 5/9ths to any thing because you are only subtracting whole numbers. thus subtract the whole numbers from the whole numbers and then "reattach" the fraction.

7 - 4 = 3
or
7 (and 5/9) minus 4 = 3 (and 5/9)

pretty simplistic in this case... don't you wish they were all like that?

Answer 5

It is not GCD but rather LCD- lowest common demoniator

for number # 1 the LCD is 10
for number # 2 the LCD is 9 since7= 7/1 and 4 =4/1