Don E Knows (joke name?) gave this answer that I thought was pretty good.
Quote: "MR is Memory Recall
MC is Memory Clear
M+ is Memory add
M- is Memory subtract
These are used to add and subtract the answers to multi-step equations so you can do the small steps with the calculator, then store, change or recall the total as needed. You might add a long string of numbers in groups this way. Or you can do all operations in one parenthesis, then just store the total of each.
A good problem to illustrate this would be : (123 x 3) + (55 - 24) + (10^2) - (7 x 8) = ???
Using MR, M+ and M-, you can do each one as a group, and only store the answers. 123 x 3 = 369 so M+ to put 369 in memory. Clear it from the calculator. 55 - 24 = 31, so M+ to put this in memory and add to the 369 already there. Clear it from the calculator. 10^2 = 100, so M+ this to memory also to add it. Clear it from the calculator. 7 x 8 = 56 so M- this to SUBTRACT it from memory. Clear it from the calculator if desired. Now, when you then hit MR, you will get the total of all of these small equations in parenthesis -- 444."
I had always ignored the memory buttons but now I will use them
Everything worthwhile requires effort.
