Reasoning · Grade 2-2 Making Four-Digit Numbers
Problem
Box 4 sits three steps along, so it is 210 above Box 1.
Skip-counting by the same amount repeatedly is just adding that amount each step, exactly like counting by 5s or 10s.
2.NBT.A.2Look For A PatternSkip-counting by the same amount three times carries Box 1 to Box 4, so the gap between them is three of those jumps.
Every box is the one before it plus the same fixed jump, so any box can be reached from an earlier one by repeating that jump.
Three jumps of the same size is three equal groups of that jump, which is what multiplying by three counts.
Adding 210 leaves the ones digit alone, so Box 1 is 1543.
Adding 210 (= 2 hundreds + 1 ten) leaves the ones digit unchanged and bumps the tens digit up by one, so I can read the missing digits backwards.
2.NBT.B.7Guess And CheckStepping on by 70 gives 1543, 1613, 1683, 1753, 1823, 1893.
Adding 70 crosses into the next hundred whenever the tens digit would pass 9, which is why 1543 jumps to 1613 and 1683 jumps to 1753.
2.NBT.B.7Look For A PatternIf you know the jump size, one number you can nail down unlocks the whole chain - just keep adding 70!