Final answer:
The angle of the sector can be found by using the formula: angle = (circumference of sector / circumference of circle) x 360 degrees. By substituting the values given (radius = 3.5 cm and length of rope = 10 cm) into the formula, we find that the angle of the sector is 60 degrees.
Step-by-step explanation:
To find the angle of the sector, we need to use the formula: angle = (circumference of sector / circumference of circle) x 360 degrees. The circumference of the sector can be found by multiplying the radius of the circle by the angle in radians. In this case, the radius is 3.5 cm and the length of the rope (circumference of the sector) is 10 cm. So the angle of the sector can be calculated as follows:
angle = (10 cm / (3.5 cm x 2π)) x 360 degrees = 60 degrees
Therefore, the size of the angle of the sector is 60 degrees, option (a).