34. Since 10 in any place is equal to 1 in the next place to the left, if the sum of the digits of any column exceeds 9, write the units' figure of the sum under the column added and carry the number of tens to the next column.

Thus, in the following example:

872

The sum of the digits in the right-hand column is 3. The sum of the digits in the second column is 16; the 6 is written under this column and the 1 is carried to the third column. The sum of the digits of the third column, together with the 1 carried to it, is 18; the 8 is written under this column and the 1 is carried to the place of thousands.

991

1863

35. Practise the following additions until you can name the results as rapidly as you can count 1, 2, 3, 4, 5, etc.

Ex. 12. (Oral.)

Add by twos to 50, beginning 0, 2, 4, 6, 8. Add by twos to 51, beginning 1, 3, 5, 7, 9.

Add by threes to 102, beginning 0, 3, 6. Add by threes to 100, beginning 1, 4, 7. Add by threes to 101, beginning 2, 5, 8.

Add by fours to 100, beginning 0, 4, 8. Add by fours to 101, beginning 1, 5, 9. Add by fours to 102, beginning 2, 6, 10. Add by fours to 103, beginning 3, 7,

11.

Add by fives to 100, beginning 0, 5, 10. Add by fives. to 101, beginning 1, 6, 11. Add by fives to 102, beginning 2, 7, 12. Add by fives to 103, beginning 3, 8, 13. Add by fives to 104, beginning 4, 9, 14.

Add by sixes to 102, beginning 0, 6, 12. Add by sixes to 103, beginning 1, 7, 13. Add by sixes to 104, beginning 2, 8, 14. Add by sixes to 105, beginning 3, 9, 15. Add by sixes to 100, beginning 4, 10, 16. Add by sixes to 101, beginning 5, 11, 17.

Add by sevens to 105, beginning 0, 7, 14. Add by sevens to 106, beginning 1, 8, 15. Add by sevens to 100, beginning 2, 9, 16. Add by sevens to 101, beginning 3, 10, 17. Add by sevens to 102, beginning 4, 11, 18. Add by sevens to 103, beginning 5, 12, 19. Add by sevens to 104, beginning 6, 13, 20.

Add by eights to 104, beginning 0, 8, 16. Add by eights to 105, beginning 1, 9, 17. Add by eights to 106, beginning 2, 10, 18. Add by eights to 107, beginning 3, 11, 19. Add by eights to 100, beginning 4, 12, 20. Add by eights to 101, beginning 5, 13, 21. Add by eights to 102, beginning 6, 14, 22. Add by eights to 103, beginning 7, 15, 23.

1

Add by nines to 108, beginning 0, 9, 18. Add by nines to 100, beginning 1, 10, 19. Add by nines to 101, beginning 2, 11, 20. Add by nines to 102, beginning 3, 12, 21. Add by nines to 103, beginning 4, 13, 22. Add by nines to 104, beginning 5, 14, 23. Add by nines to 105, beginning 6, 15, 24. Add by nines to 106, beginning 7, 16, 25. Add by nines to 107, beginning 8, 17, 26.

36. Practise adding columns of three digits until you can name the sum of any three digits the instant you see

8

9

6

5

37. The quickest way to add columns of four or more digits is to train the eye to see at a glance sums of 20, and simply add these sums. If you add the column given in the margin by single digits, you say to yourself, ten, thirteen, seventeen, twenty-two, twentyeight, thirty-seven, forty-five; if you add by taking two digits at a time, you say ten, seventeen, twentyeight, forty-five; if you add by taking three digits at 3 a time, you say thirteen, twenty-eight, forty-five; if you add by 20's, you say twenty (separating 5 into 3 and 2), forty-five.

4

8