To find out how many triangular flower beds can be laid in the rectangular field, we need to calculate the area of the field and the area of each triangular flower bed.

The area of the rectangular field is given by the formula: length * width = 24 m * 15 m = 360 m^2.

The area of each triangular flower bed is given by the formula: (1/2) * base * altitude = (1/2) * 3 m * 4 m = 6 m^2.

To find out how many triangular flower beds can be laid in the field, we divide the area of the field by the area of each triangular flower bed: 360 m^2 / 6 m^2 = 60.

Therefore, 60 triangular flower beds can be laid in the rectangular field.