how do i solve this math problem. 2/5 + 3/8 - 3/4 with the answer ending up 1/40 ?????

For any fraction additiong problems, the first step is to convert all the fractions to have the same denominator. In order to do that, you must find the lowest common denominator. You have to find the lowest number that is a multiple of 5, 8 and 4.

You can make a list to check what it is:

5-8-4

10-16-8

15-24-12

20-32-16

25-40-20

30-x-24

35-x-28

40-x-32

x-x-36

x-x-40

From the list, you can tell it is 40. Using this method, you have to multiply both the denominator and the numerator by the same number in order to obtain 40 as the denominator.

For 5, you must multiply it by 8 to get 40. Therefore, you must multiply the 2 by 8 as well. Do the same for the rest.

2*8/5*8+3*5/8*5-3*10/4*10

=16/40+15/40-30/40

=31/40-30/40

=1/40

First find the common denominator of each fraction. This happens to be 40 because each denominator divides evenly into it.

Now, change each fraction so that the denominator is 40. For the first one, you know that 5*8= 40, so you would multiply 2, which is the numerator by 8 too. You would get the fraction 16/40.

You continue to do this for the other fractions.

It would become:

(16/40)+(15/40)-(30/40)

Now, since all the denominators are the same, tou just add/subtract normally with the numerators. So you do 16+15-30, which gives you 1.

So your final answer is 1/40.

I hope that was helpful! =]

Multiply out the fractions to the lowest common denominator (in this case 40) and you get 16/40 + 15/40 - 30/40 = 1/40.

first u would have

2/5 +3/8 - 3/8=

(2/5 + 3/8) -3/8

brackets mean u do those first

then u would have

16/40 +15/40

=31/40

the u have

31/40 - 3/4

31/40 - 30/40

=1/40

remember 40 is the LCM which means lowest common multiple of 5, 8 and 4.lowest common multiple is the lowest number that is a multiple of both. so that is how i got 1/40.

change all the denominators of the fractions into 40, because that is the least common multiple. then you will get:

16/40 + 15/40 - 30/40

31/40 - 30/40

1/40

You need to make the denominator equal in all three fractions, so it'll become:

16/40 + 15/40 - 30/40.

= 31/40 - 30/40

= 1/40

you'de have to get the gcd, 40. then it would be 16/40+15/40-30/40. then that answer in easier terms is (16/40+15/40), which equals 31/40, minus 30/40=1/40.

since your adding and subtracting you need a common denominator and then you just add or subtract the numerators and you leave the denominators

2/5+3/8-3/4

16/40+15/40-30/40

31/40-30/40

1/40

16/40+15/40-30/40

1/40

I agree with you. This site is all about helping. We might be "helping" them by doing their homework, but the most important point is for them to learn. One thing I don't concur with is showing them how to solve a similar problem. A single problem will suffice. Thanks, this question really helped out.