# 1 Answer

-7/9 + 3/7

In order to add these two fractions, they must have a common denominator (9 and 7 are the denominators) When I think of a fraction, I think of the denominator being the number of pieces one whole thing has (i.e. the pie was cut into 9 pieces or 7 pieces).

The numerator is the number on top and to me represents how many of those pieces I have. In 3/7, I have three of the seven pieces of the whole one thing.

In the other fraction, I am missing two pieces completely, and I owe the other seven pieces to someone else, meaning I have less than 0 pieces of the whole thing (I know that is kinda "out there", but it makes sense to me).

I have to find a number that has both 7 and 9 as a multiple. 9, 18, 27, 36, 45, 54, 63 are multiples of 9. 7, 14, 21, 28, 35, 42, 49, 56, 63 are multiples of 7. The first number that has both as a multiple is 63. That will be my common denominator.

In order to get the /7 to 63, I had to multiply 7 x 9. I need to multiply the 3 by 9, also, to keep my fraction "the same". So 3/7 becomes 27/63.

Likewise, I had to multiply my denominator, 9, by 7. I need to multiply the 7 by 7 also, again to keep my fraction "the same." So -7/9 becomes -49/63.

NOW I can complete the equation by perfomring the addition. The denominator will remain 63. I need to add my numerators to find out how many pieces I have. 27 + (-49) = -22. The answer to the qustion is - 22/63. This fraction is stated in its lowest possible terms.

I apologize for going into so much detail. I love explaining math that is not too advanced. I hope nobody thinks I think I am a know-it-all. One thing I DO know is that I DON'T know everything!

10 years ago. Rating: 1 | |