What were the limitation of debereiner's law of traid

Dobereiner could find only three triads; . i.e total of 9 elements only. However the total number of elements were more than that of those encompassed in Dobereiner's Triad. Thus, Dobereiner's could not be classify most of the elements known at that time

 if it takes 1 and 3/4 cups to make 1 batch how many cups will it take to make 2 and 1/2 batches. 4.375 cups = x. You can also add the cups one batch and then a half batch at a time. 7/4 + 7/4 + (7/4*1/2) = x. multiply the first two (7/4) by 2/2. Then you have 14/8 + 14/8 + 7/8 = 35/8 = 4.375 cups.