how do you divide fractions???(ex. 2/5 divided by -3/10)?

Question

also example: (3 times 2.4) divided by 14???)



okay guys im having alot of trouble with algebra on my mideterm coming up, i have A's in everything except, a "d" in algbra!!!ive never on any report card or midterm ever got below a "b"!!!!! im strugglin!!! what can i do (cant afford a tutor!!!!)

Answer 1

Dividing fractions is really easy if you put one over the other and just fold them (like a sandwitch). Let me explain:

Say you want to divide 2/5 by 3/10. Just write it like this: 2/5/3/10 and fold: (2*10)/(5*3) = 20/15. Voila you have your answer.

What if one of the numbers is a whole number? You just put it over 1. So 2/5 divided by 3 is the same as 2/5 divided by 3/1.

This method is a lot easier than trying to remember which fraction to flip.

When multiplying by decimals you just multiply as if there were two regular numbers and move the decimal point to the position it was already in. So 3 times 2.4 can be solved by multiplying 3 by 24 which is equal to 72 (easy way to figure that out is to multiply 3 and 20 and add that to 3 times 4) and then moving the decimal in by one, so 3*2.4=7.2.

I hope that helps!

Answer 2

I am presuming you are not allowed to use a calculator, otherwise this problem would be too easy. To divide a fraction, you must multiply by its inverse. Let me clarify.
a/b / c/d would become a/b x d/c. All you need to do is flip the one that you are dividing by over and multiply by it. And multiplying fractions is much easier than adding them. Just multiply the top and the bottom. You don't need any common denominators or anything like that.

For your example, 2/5 divided by -3/10 becomes simply 2/5 times -10/3 (The negative sign is always written on top.) 2 x -10 is -20. 5 x 3 is 15. So you have -20/15. Now you need to simplify. Divde both by 5 and you have -4/3. If you need it written in proper form, it would be -1 1/3. Easy, no?

Your second question, 3 x 2.4, is not as hard as it looks. Forget the decimal and just multiply the two numbers.

3 x 24= 72.

Then insert the decimal in the answer. Since you only had one decimal point in the problem, you only need one in the answer. Your answer, then is 7.2.

If you had a more complex problem, like 3.15 x 2.85 you would follow the same procedure of ignoring the decimal until the last step when you would insert it four places in, since there are four values less than one in the problem.

7.2/14 is not very hard either. You can know just by looking at it that it will be around .5, since 7 is half of 14. So keep that in mind.

Convert them into fractions. 7.2 is the same as 7 and 2/10 or 7 1/5. 7 1/5 can be expressed as 36/5. Using the steps from before, multiply 36/5 by 1/14. The answer will be 36 over 70, or 18/35.

I hope this helps.

Answer 3

Flip one of the fractions and multiply. So if you're doing 2/5 and -3/10, the reciprocal (flip) of -3/10 will be -10/3.

Then go as normally:

2 10 20
- x - = --
5 3 15

So the answer to 2/5 divided by -3/10 would be -20/15 or -1 1/4 simplified.

So just flip one of the fractions so the bottom number is on the top and multiply across. Then remember to simplify!

Answer 4

For this type of problem, the simplest way is to take the 2/5 and multiply by the reciprocal of -3/10.
Set up looks like 2/5*10/-3

Multiply 2* 10 and divide the result by 5*-3

Result is 20/-15

The second problem is done in two steps;
Multiply 3*2.4=(3*.4)+(3*2)=1.2+6=7.2

Divide by 14 is a long division problem. long division is really easy, if worked the same way each time.
_______
The standard form would be 14)7.2

With the 7.2 Move the decimal point outside the form as follows

. _.____
. 14 )7.2

In this case, guess how many times 14 goes into 72
If my first guess was 5

. _.5__
. 14 )7.2 Multiply the 14 times 5 to get 70 to subtract from
. -70
. ---------
. 2
Add a zero to the 7.2 and the 2 to get 20

. .5
. ---------
. 14)7.20
. -70
. ------------
. 20

Guess the number of times 14 goes into 20

My guess is 1

. .51
. --------------
. 14)7.20
. -70
. ----------
. 20 Multiply 1 times 14 and subtract as before
. -14
. --------
. 6
You can continue in the same manner. The answer is;
.51428...
The method changes if the number you are dividing by is in the hundreds. You have to add 2 zeros for each time you add zeros. Likewise, if the number is in the thousands, add 3 zeros every time.
I hope this helps. It is really hard to make the forms.

Answer 5

In arithmetic I was taught "invert (the divisor) and multiply"
So, (2/5) / (-3/10) = (2/5)*(10/-3) = (2/1)*(2/-3) = 4/-3

With algebra, you can prove this works all the time.

x=(2/5)/(-3/10)
thinking of (-3/10) as a "unit", multiply both sides by it:
x*(-3/10) = (2/5)*(-3/10)/(-3/10)
(-3/10)/(-3/10)=1, so
x*(-3/10) = (2/5)
x*(-3/10)*(10/1) = (2/5)*(10/1)
x*(-3) = (2/5)*(10/1)
x*(-3)*(1/-3) = (2/5)*(10/1)*(1/-3)
x = (2/5)*(10/-3)
...works every time unless you try to divide by 0!

(3*2.4)/14??? leads me to believe you are toying with us.

Both of these problems are arithmetic problems, not algebra problems.

Answer 6

You can flip the second one and change the division to multiplication.
i.e. 2/5 div. -3/10 becomes 2/5 * -10/3.
Then just multiply the numerators (2*-10= -20) andthe denominators (5*3=15) separately, and put them back into a fraction (-20/15). Then just factor... -20/15 = -4/3 = -1 and 1/3.

Answer 7

reverse the 2nd fraction and multiply it by the first
for example if ur given the problem 2/5 divided by -3/10

to solve it keep the 2/5 the same and multiply it by -10/3

so u have 2/5 times -10/3 which is -20/15 or -4/3

Answer 8

well first go like this
1.2/5 divided by -3/10 leave the question alone first
2.then flip the second fraction
3.it should look like this: 2/5 diveded by -3/10
4.instead of dividing multiply :2/5 times -3/10
5.multiply the numerator by the other numerator, and then multiply the denominator by denominator.
6.you should get the answer

Answer 9

hello again. First you make it multiplication and flip -3/10. So it becomes 2/5 times 10/-3. As so u multiply. 2x10 equals 20 and 5x-3 equals -15 so it is 20/-15. The answer is -1 1/3

Answer 10

for dividing multiply by the reciprocal
(2/5)(-10/3)=-20/15=-4/3