Can someone help me with my math?!?

Question

What are the common denominators or

21 and 49

35 and 30

81 and 63

and 45 and 3

Answer 1

Rather than tell you all the answers, you need to know how to solve each problem.

go here and learn

http://www.mathsisfun.com/numbers/common...

Answer 2

i think those 3 have it covered. please vote best answer. please. my best answer ratio is only three percent!!!!!!!!!!

Answer 3

The Common Denominators of those are:

7

5

9

3

Hope  this helps

Answer 4

I assume you actually mean "least common denominator" aka "least common multiple".  I'll do the first set: 21 and 49:

1) first you take the prime factorization of each number:

21= 7 X 3, 49 = 7^2

2) next you write down the factors that exist in EITHER number:

21 has 7 and 3, 49 has 7 only...so we know the LCD is going to be some variation of 7 X 3.

3) next you look at the exponents.  3 appears only in 21 and has an exponent of 1, so you know it'll be 3 to the first.  7 appears in both 21 and 49, but the 7 in 49 has an exponent of 2, so it'll be 7^2.

4)finally, you multiply it out:  3X7^2= 147

NB: when writing on the computer the ^ is used to indicate "raised to the power of" so 3^3 is the same as saying 3X3X3.

Answer 5

7, 5, 9 and 3.  I'm pretty certain of that.

X

Answer 6

7

5

9, 3

3

Answer 7

7 5 9 3 seriously that's like 5th grade stuff cant you use a denominator tree there so easy

Answer 8

the common denominators are

7

5

9

3

Answer 9

7

5

9

3

Answer 10

never

Answer 11

No, no and no!  Many are misreading the question so far!

You want COMMON denominators for the fractions

1/b and 1/c where b and c are any of your pairs.

So for 21 and 49 we want to find the least common denominator

for 1/21 and 1/49.

The way to do this is to find the product of the 2 numbers

and divide by their greatest common factor.

So the least common denominator for 1/21 and 1/49

is 21*49/7 = 21*7 = 147.

Similarly for 1/35 and 1/30

we get 35*30/5 = 35*5 = 175.

Now you try the last two!

Answer 12

21=7*3

49=7*7

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

cd=7

35=7*5

30=2*3*5

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

cd=5

81=3*3*3*3

63=7*3*3

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

cd=3*3=9

45=3*3*5

3=3

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

cd=3