In regards to the braille system(6 dots that can either be raised or not raised), how many symbols have exactly three raised dots?
I figured it would be C(6,3) but 20 seems a bit off??
Thanks in advance
looks good to me -- they can be
123
124
125
126
134
135
136
145
146
156
234
235
236
245
246
256
345
346
356
456