Draw a circle, and label the center.
Draw the radius of 26m, diameter of 52m.
Now draw a chord of 48m. Half the chord is 24m. These lines should be parallel.
Draw a line from the center to the point where the chord touches the circle.
Now draw a line perpendicular to the diameter and the chord at the point where the chord and circle intersect.
You've now created a right triangle where the hypothenuse is the diagonal line from the circle center to the point where the chord meets the circle. It's measure is 26m. The base of the triangle is half the chord, 24m. And, the height of the triangle is the distance between the diameter/radius and the chord. This is what we need to find, x.
Use the pythagorean theorem to solve
x2 + 242 = 262
x2 + 576 = 676
x2 = 100
x = 10
The chord is 10 m from the center of the circle.