29 cm is the right answer to this problem. To get the magnitude, first, we add all the distances or vectors covered by the ant. So, 30 cm East plus 25 cm North plus 15 cm West and we get 70 cm. That is the total distance covered by the ant from its original point to its final location.
Now, to get the magnitude, use the formula: square root of (15^2+25^2). It will be the square root of (225+625) equals the square root of 850. And lastly, get the square root of 850 that is 29.2 or 29 cm. This means that the distance between point A to point B (final point) is 29 cm.