Complete the following number patterns.
- 805, 724, 643, , 481
- 39, 49, 60, 72, .
- 172, , 189, 193, 195
(a)
805 - 724 = 81
724 - 643 = 81
643 - 81 = 562
Pattern: Keep subtracting 81 from left to right.
(b)
49 - 39 = 10
60 - 49 = 11 (1 is added to 10)
72 - 60 = 12 (1 is added to 11)
12 + 1 = 13
72 + 13 = 85
Pattern: Keep adding 1 to the previous added number from left to right.
(c)
195 - 193 = 2
193 - 189 = 4
189 - 6 = 183
183 - 11 = 172
Pattern: Keep subtracting 2 from the previous subtracted number from right to left.
Answer(s): (a) 562; (b) 85; (c) 183
