Problem number 21. Each ladybug sticker has 1, 2, 3, or 4 dots. Aaron wants to fill the grid with stickers so that in each row and in each column there are ladybugs with different numbers of dots. When Aaron is finished, what will the top row of the grid look like? To solve this problem, let's try to look at squares in the grid that are heavily restricted. For example, look at this square right here, marked with a question mark. In the row of this question mark cell, we see that there is a ladybug with 1 dot and a ladybug with 4 dots. This means that the question mark cannot have 1 or 4 dots. Similarly, in the column, we see that there is a ladybug with 3 dots. That means that this square cannot have 3 dots. That means the only possible number of dots this square can have is 2. Now we can use this logic to fill in some of the other squares in the grid. Look at this one right here. In the row, we see that there is a ladybug with 4 dots. In the column, there are ladybugs with 2 and 3 dots. This means that this cell has to have a ladybug with 1 dot, since that's the only number left out of 1, 2, 3, and 4. Finally, look at the top cell in that column. We know that in the column we already see ladybugs with 1, 2, and 3 dots. This means that this ladybug must have 4 dots. Now we can start to think about answering the question. The question asks, what will the top row of the grid look like? We already know that in the top row of the grid, there is a ladybug with 4 dots in the first square. If we look at all the options, only option A has a ladybug with 4 dots in the first square. This means that even though we haven't filled out the entire grid yet, we can be sure that none of the other options can match, so we can be sure that the answer is A. If we want to fill out the full grid, we can do so as follows, and you will see that it does match answer A, but you don't need to fill out the full grid to solve this problem. The answer is A.

ladybug stickers

grid puzzle

logical deduction

unique dots

top row solution