Each square on the grid measures 1 unit by 1 unit. Suppose you want to walk from point *A* to point *B* only moving right or up, but you have to stay on the gridlines. How many different paths can you take?

This problem is a classic example of finding the number of different paths in a grid. The key here is that you're restricted to moving only right (R) or up (U) on a grid. To solve it, we can use combinatorics.

### Problem Explanation:
Let's assume the coordinates of point **A** are \((x_1, y_1)\) and the coordinates of point **B** are \((x_2, y_2)\). The number of steps you need to take to get from **A** to **B** is determined by the difference in their coordinates:
- You need to move \( x_2 - x_1 \) units to the right.
- You need to move \( y_2 - y_1 \) units up.

If the horizontal distance is \( a \) and the vertical distance is \( b \), then every valid path consists of \( a \) rightward steps (R) and \( b \) upward steps (U). These steps can be arranged in different orders.

### Formula:
The total number of different paths is the number of ways to arrange \( a \) rightward steps and \( b \) upward steps in a sequence of \( a + b \) steps. This is given by the binomial coefficient:
\[
\binom{a + b}{a} = \frac{(a + b)!}{a! \cdot b!}
\]
where \( a \) is the number of rightward steps, and \( b \) is the number of upward steps.

### Example:
Suppose point **A** is at \((0, 0)\) and point **B** is at \((3, 2)\), meaning:
- You need to move 3 steps to the right.
- You need to move 2 steps up.

The number of different paths is:
\[
\binom{3 + 2}{3} = \frac{(3 + 2)!}{3! \cdot 2!} = \frac{5!}{3! \cdot 2!} = \frac{120}{6 \cdot 2} = 10
\]
Thus, there are 10 different paths from **A** to **B**.

Would you like to go through more examples or further details on how to calculate this?

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Here are 5 relative questions:
1. What if you can move left or down as well as right or up?
2. How does the formula change if obstacles are placed on the grid?
3. What if the grid has different dimensions, like unequal horizontal and vertical distances?
4. How can this concept be extended to 3D grids (right, up, and forward)?
5. Can you explain how Pascal's Triangle relates to this combinatorial problem?

**Tip**: For problems involving grids, break them down into simple movements and then apply combinatorics for the solution!

Each square on the grid measures 1 unit by 1 unit. Suppose you want to walk from point A to point B only moving right or up, but you have to stay on the gridlines. How many different paths can you take?

Learn how to calculate the number of different paths from point A to point B on a grid where movement is restricted to the right and up. Using combinatorics and the binomial coefficient formula, this detailed explanation is suitable for students in Grades 9-12.

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