Howcome -0.4 + 1 = 6 ?

Question

After doing some practice math problems I came across one that was difficult. It was too hard so I used a calculater ro find the answer to -0.4 +1... and the answer was positive 0.6! Howcome?

Answer 1

Hi Aimond--

 

It's because you're

 

a) counting by 10ths

 

b) working with absolute value, which is a distance from a zero point.

 

Draw a number line with a 0 in the middle, so that you have room on both the negative and positive sides.

 

Make little hash marks on the positive side AND the negative side so that it goes UP to 10/10ths and DOWN to negative 10/10ths. There should be one hashmark for each 10th, in each direction.

 

Now, find the -4/10 mark. Now count in the positive direction, and go up 10 of the hashmarks--you just counted to 1, going by 10ths, and you ended up at 6/10ths

 

So negative 4/10s, plus 10/10ths, equals 6/10ths

 

Hope this helps!

 

Matt

Answer 2

Adding a negative number (in this case, -0.4) is the same as subtracting a positive number:

 

(-0.4) + 1 = 1 + (-0.4) = 1 - 0.4 = 0.6