Island Hopping By Ones & Tens
A rectangular grid of numbers is given with some numbers filled in. Fill in the remaining numbers so that any two numbers that share a side only differ in a single place, and the difference of the digits in that place is 1 (including going between 0 and 9). No number may be used more than once. Using a 100-Chart may be helpful for beginning solvers.
How to create
Take an empty grid and fill it with numbers, with no number repeated. Next, remove some of the numbers. In the example, the red numbers are the missing ones.
Bonus Material
A rectangular grid of numbers is given with some of the numbers filled in. The challenge is to fill in the remaining numbers so that any two numbers that share a side only differ in a single place, and the difference of the digits in that place is 1 (including going between 0 and 9). No number may be used more than once in the entire grid. Referencing a 100-Chart may be helpful for beginning solvers.
Make this puzzle by taking an empty grid and filling it with numbers, with no number repeated. Next, remove some of the numbers, making sure that it is not too hard for your child. In these examples, the red numbers are the missing ones.
Using only one-digit and two-digit numbers, there is not a lot of trickiness that can be introduced. However, they are great practice for thinking about place value. One wrinkle that may surprise your child are transitions such as 95 to 5 to 15 or 11 to 10 to 0 to 9 – they may not realize there is a 0 in the tens place for single-digit numbers and they may be surprised by 0 and 9 being connected.
Grids are a natural way to present these problems. However, the puzzles can also be represented in the same way as other Island Hopping puzzles using circles, and this representation allows for some additional freedom in creating puzzles.
Helping your child
Puzzles are meant to be challenging and to take time, so please don’t ruin the fun by telling your child how to do them. These puzzles are chosen so that you can create them easily and then have fun solving them together.
If your child gets stuck on a puzzle, you have several options. You can, of course, give very small hints, if you can think of things that won’t give away the puzzle. You can suggest looking at smaller or simpler versions of the puzzle. Encourage your child to be bold in their ideas, even if sometimes they lead to dead ends. We all learn a lot from our mistakes and dead ends! Let your child know that it is perfectly okay not to solve a puzzle on the first (or second or third) try, and that useful ideas may occur to them if they leave the puzzle alone for a day or two.
These puzzles are meant to be fun and to teach problem solving. One of the greatest mathematical pleasures is that AHA moment, after many false starts and much wrestling with a problem, when the answer is finally discovered – be sure to let your child experience that feeling of discovery as many times as you can!