The Psychology of Arithmetic

by Edward L. Thorndike

5. Count by 25s to $2.50, saying, "25 cents, 50 cents, 75 cents, one dollar," and so on.

6. Count by 15s to $1.50.

7. Find the products. Do not use pencil. Think what they are.

A.	B.	C.	D.	E.
2 × 25	3 × 15	2 × 12	4 × 11	6 × 25
3 × 25	10 × 15	2 × 15	4 × 15	6 × 15
5 × 25	4 × 15	2 × 25	4 × 12	6 × 12
10 × 25	2 × 15	2 × 11	4 × 25	6 × 11
4 × 25	7 × 15	3 × 25	5 × 11	7 × 12
6 × 25	9 × 15	3 × 15	5 × 12	7 × 15
8 × 25	5 × 15	3 × 11	5 × 15	7 × 25
7 × 25	8 × 15	3 × 12	5 × 25	7 × 11
9 × 25	6 × 15	8 × 12	9 × 12	8 × 25

State the missing numbers:—

A. 36 = .... 12s	B. 44 = .... 11s	C. 50 = .... 25s
60 = .... 12s	88 = .... 11s	125 = .... 25s
24 = .... 12s	77 = .... 11s	75 = .... 25s
48 = .... 12s	55 = .... 11s	200 = .... 25s
144 = .... 12s	99 = .... 11s	250 = .... 25s
108 = .... 12s	110 = .... 11s	175 = .... 25s
72 = .... 12s	33 = .... 11s	225 = .... 25s
96 = .... 12s	66 = .... 11s	150 = .... 25s
84 = .... 12s	22 = .... 11s	100 = .... 25s

Find the quotients and remainders. If you need to use paper and pencil to find them, you may. But find as many as you can without pencil and paper. Do Row A first. Then do Row B. Then Row C, etc.

Row A.	11|45	12|45	25|45	15|45	21|45	22|45
Row B.	25|55	11|55	12|55	15|55	22|55	30|55
Row C.	12|60	25|60	15|60	11|60	30|60	21|60
Row D.	12|75	11|75	15|75	25|75	30|75	35|75
Row E.	11|100	12|100	25|100	15|100	30|100	22|100
Row F.	11|96	12|96	25|96	15|96	30|96	22|96
Row G.	25|105	11|105	15|105	12|105	22|105	35|105
Row H.	12|64	15|64	25|64	11|64	22|64	21|64
Row I.	11|80	12|80	15|80	25|80	35|80	21|80
Row J.	25|200	30|200	75|200	63|200	65|200	66|200

Do this section again. Do all the first column first. Then do the second column, then the third, and so on.