3.
a. 380 ÷ 38 = 10
b. 190 ÷ 38 = 5
c. 570 ÷ 38 = 15
d. use 10 times 38 = 380, 190 is half of 380 so half of 10 is 5, 570 is 380 + 190 so 10 + 5
4.
a. 670 ÷ 67 = 10
b. 603 ÷ 67 = 9
c. 737 ÷ 67 = 11
d. use 10 times 67 = 670, 603 is 670 - 67 so 10 - 1 = 9, 737 is 670 + 67 so 10 + 1 = 11
Challenge:
1062 - 279 = 783
783 - 261 = 522
522 ÷ 15 = 34 remainder 12
So she put 34 books in each box