Edmund leaves and walks 15 km due south from school, turns and walks 20 km west to get to work.How far would Edmund need to walk in a straight line to get back to school?

To solve this problem, we can use the Pythagorean theorem because the path that Edmund took forms a right triangle. The Pythagorean theorem states that in a right triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the lengths of the other two sides. This can be written as: a² + b² = c².

Here's the step-by-step solution:

1. Identify the lengths of the two sides of the right triangle. In this case, the two sides are the paths that Edmund walked: 15 km south and 20 km west. So, a = 15 km and b = 20 km.

2. Substitute the values of a and b into the Pythagorean theorem: (15 km)² + (20 km)² = c².

3. Calculate the squares: 225 km² + 400 km² = c².

4. Add the squares: 625 km² = c².

5. Take the square root of both sides to solve for c (the straight-line distance from work back to school). The square root of 625 km² is 25 km.

So, Edmund would need to walk 25 km in a straight line to get back to school from work.