[mamelukesabre]

It aint' that hard to figure 15 percent.

you can do 10 percent, can't you??

you can do 50 percent can't you??

you can add can't you??

just figure 10 percent, then figure 50 percent of that 10 percent, then add the two together. The result is 15 percent.

[dennisw]

I said exactly that in another post. That's an old math trick.

Still..... dividing the bill by 7 (to calculate a 15% tip) is quicker and just as good.