Two rules, two patterns, step by step
Two rules run side by side: add 3 along the top, add 9 along the bottom.
The question
Two rules, two patterns
row 1:5→30
row 2:10→60
row 3:15→90
row 4:20→?
row 1:5→30
row 2:10→60
row 3:15→90
row 4:20→?
row 1:5→30
row 2:10→60
row 3:15→90
row 4:20→?
row 1:5→30
row 2:10→60
row 3:15→90
row 4:20→120
- Two patterns, and each column counts in its own step — so a gap CAN be filled by counting down its own column. But that is not what a table of pairs is for: the two sides are locked to each other, and the same link works on every row.
- Read the link off a row with nothing missing. Row 1: 5 on the left, 30 on the right — that is × 6.
- The same link holds all the way down, so use it on the gap: 20 × 6 = 120.
- Counting down the column gets there too — this is not a trick — but the link is what the two patterns were put next to each other to show.
How it works.
- 01
Two patterns, and each column counts in its own step — so a gap CAN be filled by counting down its own column. But that is not what a table of pairs is for: the two sides are locked to each other, and the same link works on every row.
- 02
Read the link off a row with nothing missing. Row 1: 5 on the left, 30 on the right — that is × 6.
- 03
The same link holds all the way down, so use it on the gap: 20 × 6 = 120.
- 04
Counting down the column gets there too — this is not a trick — but the link is what the two patterns were put next to each other to show.