text: Actually, if you get really good in algebra, you can use that skill to do arithmetic better in the real world. You can do things in your head instead of on paper.\n\nHere's a really simple example: let's say that you want to buy three of something that costs $18.  Off the top of your head, you don't know what 3 x 18 is.  BUT! Algebra tells you that multiplication is associative.  So if you think of 18 as 2x9, then you can think:\n\n3 x 18 = 3 x (2 x 9)\n= (3 x 2) x 9 (that's the associative part)\n= 6 x 9\nand then you remember from your multiplication tables that 6 x 9 is 54.  So you'll pay $54.\n\nHere's a more complicated example: You're traveling for 5.5 hours at 65 miles per hour, and want to know how much distance you'll cover (distance = speed x time).\n\nWell, first, 65 x 5.5 = 65 x (55 / 10) = (65 x 55) / 10.  But now, how do you multiply 65 x 55 in your head?  Well, if you've learned about factoring in your algebra class, you can reason based on the "difference of two squares":\n\n(a+b)(a-b)=a² - b²\n\n65 x 55 = (60 + 5)(60 - 5)\n= 60² - 5² (there's the difference of two squares factoring coming into play)\n= 3600 - 25 (60 and 5 are easy to square in your head)\n= 3575 (also easy)\n\nSo 65 x 5.5 = 3575 / 10 = 357.5 miles!  And the point is that, with the algebra knowledge, you can do a lot of this in your head -- I wrote it all out for you to read, but you don't have to!