Question: DRILL & PRACTICE
Mathematics Year 5
PRACTICE 2 Find the unknown angles marked with ‘y’. Show your working steps in the spaces provided.
(1) 156°
y
position_hint: top-left; graph: three rays meet at one point: one ray goes up, one goes left, and one goes down-right, with the 156° angle between the up ray and the down-right ray and y at the lower angle.
(2) 168°
171°
y
position_hint: center-left; graph: three rays meet at one point: one ray goes left, one goes up-right, and one goes down-right, with 168° on the upper-left angle, 171° on the lower angle, and y on the right angle.
(3) 30°
46°
107°
y
position_hint: center-left; graph: four rays meet at one point: one ray goes upper-left, one goes upper-right, one goes right, and one goes lower-left, with 30° between upper-left and upper-right, 46° between upper-right and right, 107° between right and lower-left, and y on the left angle.
(4) 60°
20°
y
position_hint: bottom-left; graph: four rays meet at one point: one ray goes left, one goes up-right, one goes down-right, and one goes down, with 60° between up-right and down-right, 20° between down-right and down, and y on the upper-left angle.Help withthis plss
1. **Problem 1:** Find $y$ when three rays meet at a point with angles $156^\circ$, $y$, and the third angle.
2. The sum of angles around a point is always $360^\circ$.
3. Using the formula: $$156^\circ + y + \text{third angle} = 360^\circ$$
4. Since the three rays form a straight line with $156^\circ$ and $y$ adjacent, the third angle is $180^\circ$ (straight line).
5. So, $$156^\circ + y = 180^\circ$$
6. Subtract $156^\circ$ from both sides:
$$\cancel{156^\circ} + y = 180^\circ - \cancel{156^\circ}$$
7. Simplify:
$$y = 24^\circ$$
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1. **Problem 2:** Find $y$ given angles $168^\circ$, $171^\circ$, and $y$ around a point.
2. Sum of angles around a point is $360^\circ$.
3. Write equation:
$$168^\circ + 171^\circ + y = 360^\circ$$
4. Add known angles:
$$339^\circ + y = 360^\circ$$
5. Subtract $339^\circ$ from both sides:
$$\cancel{339^\circ} + y = 360^\circ - \cancel{339^\circ}$$
6. Simplify:
$$y = 21^\circ$$
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1. **Problem 3:** Find $y$ given four angles around a point: $30^\circ$, $46^\circ$, $107^\circ$, and $y$.
2. Sum of angles around a point is $360^\circ$.
3. Write equation:
$$30^\circ + 46^\circ + 107^\circ + y = 360^\circ$$
4. Add known angles:
$$183^\circ + y = 360^\circ$$
5. Subtract $183^\circ$ from both sides:
$$\cancel{183^\circ} + y = 360^\circ - \cancel{183^\circ}$$
6. Simplify:
$$y = 177^\circ$$
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1. **Problem 4:** Find $y$ given four angles around a point: $60^\circ$, $20^\circ$, and $y$ plus one unknown angle.
2. Sum of angles around a point is $360^\circ$.
3. The unknown angle adjacent to $y$ and $60^\circ$ and $20^\circ$ is $y$'s supplementary angle.
4. Write equation:
$$60^\circ + 20^\circ + y + \text{unknown angle} = 360^\circ$$
5. Since the unknown angle and $y$ are adjacent and form a straight line, their sum is $180^\circ$:
$$y + \text{unknown angle} = 180^\circ$$
6. Substitute into total sum:
$$60^\circ + 20^\circ + 180^\circ = 360^\circ$$
7. Add:
$$260^\circ = 360^\circ$$
8. This is not possible unless $y$ and unknown angle sum to $180^\circ$ and the rest sum to $180^\circ$.
9. So, $y$ is supplementary to $60^\circ + 20^\circ = 80^\circ$:
$$y = 180^\circ - 80^\circ = 100^\circ$$
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**Final answers:**
1. $y = 24^\circ$
2. $y = 21^\circ$
3. $y = 177^\circ$
4. $y = 100^\circ$