looking at https://en.wikipedia.org/wiki/E6B it looks like it would be very difficult to calculate, say, 124 × 53 × √14500 ÷ 0.77 on an e6b; it seems to only have two general-purpose scales and no cursor

on a standard linear slide rule, the most obvious way to do this calculation takes five moves:

- move the slide to align the left d scale index with 1.24 on the c scale;

- move the cursor to 5.3 on the d scale, thus putting it at the position of 6.57 on the c scale, which you know means 6.57 thousand;

- move the left index of the d and b scales to the cursor;

- move the cursor to 1.45 (not 14.5!) on the b scale, thus putting it at the position of 7.91 on the c scale, which you know means 7.91 hundred thousand;

- move the slide to align 7.7 on the d scale with the cursor;

- read the answer, 1.028, off the c scale at the left index of the d scale, which you know means 1.028 million. (the 6.57 was an approximation of 6.572 because on a normal-sized slide rule you can't read things off to four significant figures that far up the scale, but you can definitely tell 1.028 apart from 1.025 or 1.030, though possibly not 1.027 or 1.029)

i think you can do this same calculation in just three moves by using the ci and di scales (and maybe a instead of b), or using cf, df, and cif for some of the calculation, but i never learned how to use a slide rule properly because i was born after the hp-35; hopefully someone who was born before 01960 reads this thread and can explain a better way to do it

you can do this with just c, d, and l scales if you have to, but it takes some mental work (and extra moves) for the square root. at a given length, circular slide rules are better because they save you from having to choose between the left and right indices, and their maximum dimension is smaller, being almost τ times smaller than a linear slide rule of the same length — but they also tend to weigh more

looking at https://upload.wikimedia.org/wikipedia/commons/c/c4/StudentE..., the e6b seems to have c and d scales (this is an edit correcting my earlier version of comment, which claimed it didn't). they're the scales in this photo that say 'imp. gal.' at the top. but for taking a square root i think you're on your own, and it doesn't seem to have a cursor, which is a significant drawback. and i'm skeptical of the play in the grommet used as the pivot; it seems like that could really hurt your significant figures

so, probably do not buy an e6b in order to learn about slide rules; you will be almost as disappointed as if you bought it in order to learn about computers