Educational worksheet for identifying right angles in objects and classifying angles.

Problem Analysis and Solution

The image contains two tasks related to angles. Let's solve each task step by step.

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#### Task 1: Put a cross (×) for objects that have right angles in them.

We need to identify which of the given objects contain right angles (90° angles). A right angle is formed when two lines or edges meet at a 90° angle.

##### Objects:
1. Book: A book has rectangular faces, and rectangles have four right angles.
2. Dice: A dice is a cube, and cubes have right angles at their edges.
3. Brick: A brick is typically rectangular in shape, so it has right angles.
4. Triangle sign: This is a triangular warning sign, and triangles do not necessarily have right angles unless specified.
5. Tent: A tent is generally triangular in shape and does not have right angles.
6. Easel: An easel often has a rectangular base and supports, so it has right angles.
7. Ruler: A ruler is a straight edge and does not form angles on its own.
8. Clock: A clock face is circular, and circles do not have right angles.

##### Solution:
- Book: ×
- Dice: ×
- Brick: ×
- Triangle sign:
- Tent:
- Easel: ×
- Ruler:
- Clock:

Final Answer for Task 1:
- Book: ×
- Dice: ×
- Brick: ×
- Triangle sign:
- Tent:
- Easel: ×
- Ruler:
- Clock:

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#### Task 2: Label each angle as right, acute, or obtuse.

We need to classify each angle based on its measure:
- Right angle: Exactly 90°.
- Acute angle: Less than 90°.
- Obtuse angle: Greater than 90° but less than 180°.

##### Angles:
1. Angle \( a \): This angle appears to be exactly 90°.
2. Angle \( b \): This angle appears to be less than 90°.
3. Angle \( c \): This angle appears to be greater than 90°.
4. Angle \( d \): This angle appears to be greater than 90°.
5. Angle \( e \): This angle appears to be less than 90°.
6. Angle \( f \): This angle appears to be greater than 90°.

##### Solution:
- Angle \( a \): Right
- Angle \( b \): Acute
- Angle \( c \): Obtuse
- Angle \( d \): Obtuse
- Angle \( e \): Acute
- Angle \( f \): Obtuse

Final Answer for Task 2:
- \( a \): Right
- \( b \): Acute
- \( c \): Obtuse
- \( d \): Obtuse
- \( e \): Acute
- \( f \): Obtuse

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Final Answers:

1. Task 1:
- Book: ×
- Dice: ×
- Brick: ×
- Triangle sign:
- Tent:
- Easel: ×
- Ruler:
- Clock:

2. Task 2:
- \( a \): Right
- \( b \): Acute
- \( c \): Obtuse
- \( d \): Obtuse
- \( e \): Acute
- \( f \): Obtuse

Boxed Final Answer:
\[
\boxed{
\text{Task 1: Book, Dice, Brick, Easel; Task 2: } a = \text{Right}, b = \text{Acute}, c = \text{Obtuse}, d = \text{Obtuse}, e = \text{Acute}, f = \text{Obtuse}
}
\]