```

Molarity (M) = moles of solute / liters of solution

```

First, we need to calculate the moles of potassium bromide (KBr) dissolved in the solution:

```

Moles of KBr = mass of KBr / molar mass of KBr

```

The molar mass of KBr is approximately 119.0 g/mol.

```

Moles of KBr = 26.3 g / 119.0 g/mol = 0.221 mol

```

Next, we need to convert the volume of the solution from milliliters (mL) to liters (L):

```

Volume of solution = 487 mL = 0.487 L

```

Now we can calculate the molarity of the solution:

```

Molarity (M) = 0.221 mol / 0.487 L = 0.454 M

```

Therefore, the molarity of the solution obtained when 26.3 g potassium bromide are diluted to 487 mL is 0.454 M.