a.

90°. Sample response: The two hands make a right angle. (Students may also say 270°, and that there is a right angle and a big angle that together make 360°.)
150° (and 210°). Sample response: At 1 o’clock, the hour hand makes a 30° angle with the minute hand at 12 because it’s \(\frac{1}{12}\) of the circle or \(\frac{1}{12}\) of 360°. There are 5 of the angles that make up the angle that the hands make at 5 o’clock. So their angle is \(5\times30\) or 150°.
180°. Sample response: The two hands make a straight line, or half of a 360° angle.

b. 120°. Sample response: There are 360° in the full circle and 3 groups of 4 hours, so one group of 4 hours must be \(360\div3\), which is 120.

4.7.C Practice Problem 4 Scoring Guidance