I think this is a fraction? It's: 4 (-2.5) Trying to get the answer

[khi200]

Hi, I've been working on this problem: 4(-2.5) for some time for my homework, but I can't seem to figure out how to get the correct answer. According to a website, the answer to the math question is -10 but it doesn't explain how it got that answer in the first place. I end up getting a different answer than -10 so I'm under the impression that I'm not doing the problem correctly.
I need some help with it. Can someone please explain how I can get the correct answer?

I have a picture of what I've been doing on paper and a screenshot of the website explaining the problem to me.
Feel free to look at it, and give me some feedback and guidance. Thank you all.

 

[Otis]

2.5 is the decimal form of the mixed number 2½.

2½ = 2 + ½

2.5 = 2.0 + 0.5

0.5 is the decimal form of ½, yes? That is, 0.5 is 5/10, which reduces to ½.


Using your (distributive) approach, we don't multiply 4×5. We multiply 4×0.5

In other words:

(-4)(2.5) = (-4)(2 + 0.5) = (-4)(2) + (-4)(0.5) = (-8) + (-2) = -10


You could also multiply 4×2.5 using longhand multiplication; remember to put a negative sign in front of the result.


You could also switch to rational form, by rewriting 2.5 as an improper fraction and then cancelling the common factor of 2 (before multiplying the two fractions).

\(\displaystyle \dfrac{-4}{1} \cdot \dfrac{5}{2} = \dfrac{-2}{1} \cdot \dfrac{5}{1} = \dfrac{-10}{1}\) :cool:

 

[Harry_the_cat]

Hi, I've been working on this problem: 4(-2.5) for some time for my homework, but I can't seem to figure out how to get the correct answer. According to a website, the answer to the math question is -10 but it doesn't explain how it got that answer in the first place. I end up getting a different answer than -10 so I'm under the impression that I'm not doing the problem correctly.
I need some help with it. Can someone please explain how I can get the correct answer?

I have a picture of what I've been doing on paper and a screenshot of the website explaining the problem to me.
Feel free to look at it, and give me some feedback and guidance. Thank you all.

4 x 2.5 = 4 lots of 2.5 = 2.5 + 2.5 +2.5 + 2.5 =10

Therefore 4 x -2.5 = -10

 

[topsquark]

Hi, I've been working on this problem: 4(-2.5) for some time for my homework...

A suggestion: When doing Mathematics use fractions not decimals. It's just a good practice to keep.

-Dan

 

[Steven G]

Hi, I've been working on this problem: 4(-2.5) for some time for my homework, but I can't seem to figure out how to get the correct answer. According to a website, the answer to the math question is -10 but it doesn't explain how it got that answer in the first place. I end up getting a different answer than -10 so I'm under the impression that I'm not doing the problem correctly.
I need some help with it. Can someone please explain how I can get the correct answer?

I have a picture of what I've been doing on paper and a screenshot of the website explaining the problem to me.
Feel free to look at it, and give me some feedback and guidance. Thank you all.

2.5 = 2.50 so think $2.50. If you buy 4 items that each cost $2.50, then how much do you pay for the items? you really should now this answer, Sure you should know how to compute this by hand and a few methods have been given already. Study them.