The Psychology of Arithmetic

by Edward L. Thorndike

Fig. 13.—Same as Fig. 11, but for text C.

Fig. 14.—Same as Fig. 11, but for text D.

Fig. 15.—Distribution of practice with multipliers of the XOX type in the first two books of the three-book text A.

Fig. 16.—Same as Fig. 15, but for text B. Following this period come certain pages of computation to be used by the teacher at her discretion, containing 17 XOX multiplications.