The Psychology of Arithmetic - Edward L. Thorndike

	2	3	4	5	6	7	8	9	Total
2	226	154	162	150	97	87	66	45
12	74	53	76	46	51	37	36	33
22, etc.	50	60	68	63	42	50	38	26

3	216	141	127	89	82	54	58	40
13	43	43	60	70	52	30	22	18
23, etc.	15	30	51	50	42	32	29	30

7	85	90	103	103	84	81	61	47
17	35	25	42	32	35	21	29	16
27, etc.	30	23	32	29	24	23	25	28

8	185	112	146	99	75	71	73	61
18	28	35	52	46	28	29	24	14
28, etc.	53	36	34	38	23	36	27	27

9	104	81	112	96	63	74	58	57
19	13	11	31	38	25	14	22	11
29, etc.	19	17	27	20	32	32	19	18

2, 12, 22, etc.	350	277	306	260	190	174	140	104	1801
3, 13, 23, etc.	274	214	230	209	176	116	109	88	1406

7, 17, 27, etc.	148	138	187	164	141	125	115	91	1109
8, 18, 28, etc.	266	183	232	185	126	136	124	102	1354
9, 19, 29, etc.	136	109	170	154	120	120	99	86	994

Totals	1164	921	1125	972	753	671	687	471

TABLE 4

Amount of Practice: Subtraction Bonds in a Recent Textbook (A) of Excellent Repute. Books I and II, All Save Four Sections of Supplementary Material, to be Used at the Teacher's Discretion

Minuends	Subtrahends
Minuends	1	2	3	4	5	6	7	8	9
1	372
2	214	311
3	136	149	189
4	146	142	103	205
5	171	91	92	164	136
6	80	59	69	71	81	192
7	106	57	55	67	59	156	80
8	73	50	50	75	50	62	48	152
9	71	75	54	74	48	55	55	124	133
10	261	84	63	100	193	83	57	124	91

11		48	31	50	36	41	32	46	35
12			48	77	57	51	35	80	30
13				35	22	40	29	35	28
14					25	37	36	49	32
15						33	19	48	20

16							16	36	26
17								27	20
18									19

Total excluding 1 − 1, 2 − 2, etc.	1258	755	565	713	571	558	327	569	301

TABLE 5

Frequencies of Subtractions not Included in Table 4

These are cases where the pupil would, by reason of his stage of advancement, probably operate 35 − 30, 46 − 46, etc., as one bond.

Minuends	Subtrahends
Minuends	1 11 21 etc.	2 12 22 etc.	3 13 23 etc.	4 14 24 etc.	5 15 25 etc.	6 16 26 etc.	7 17 27 etc.	8 18 28 etc.	9 19 29 etc.	10 20 etc.
10, 20, 30, 40, etc.	11	29	16	52	32	51	7	30	22	60
11, 21, 31, 41, etc.	42	14	22	32	12	26	19	52	17	10
12, 22, 32, 42, etc.	47	97	5	13	9	21	11	24	19	17
13, 23, 33, 43, etc.	7	40	7	14	15	13	19	19	22	3
14, 24, 34, 44, etc.	8	28	14	58	13	16	14	26	19	7
15, 25, 35, 45, etc.	21	28	29	54	51	15	21	12	24	8
16, 26, 36, 46, etc.	5	18	12	27	35	69	13	17	19	2
17, 27, 37, 47, etc.	5	9	12	40	32	54	24	12	12	1
18, 28, 38, 48, etc.	2	16	10	23	22	36	18	47	16	0
19, 29, 39, etc.	5	7	7	10	13	28	14	23	16	0

Totals	153	286	134	323	234	329	160	262	186	108

TABLE 6

Amount of Practice: Multiplication Bonds in Another Recent Textbook (B) of Excellent Repute. Books I and II