The larger squares are often outlined with a darker line, while the smaller squares have a thinner line. Also, sometimes the larger squares will be colored in a checkerboard pattern.
So, if a large square already has the number “2” in it, you know it can’t include another number “2” anywhere in the square.
For example, if a larger square has numbers 1-3 and 5-9, you know it’s missing the number “4,” which you can fill in.
If a column has numbers 1-7 and 9, you know it’s missing the number “8,” which you can fill in.
If “8” is repeated in 2 squares, look for that number in the third square. Run your finger down the rows with each “8,” as you know the “8” can’t be in those rows in the third large square.
In that case, trace down the columns. See if the number you’re trying to fill in is in 1 of the columns. In that case, you know it can’t go in that column and must go in the other one.
For instance, take the number “6. " See which rows and columns already have 6s, and use that to scan across to the 3 large squares you’re looking at. Based on that information and what you have in the squares, try to place as many of the 6s as you can.
As you work, you may notice certain squares only have 1 number, and you may be able to fill in that number permanently.
As you recheck the blank spaces, go through the techniques again to help fill in numbers.
