**Class 6 Mathematics Chapter 5|**

**Understanding Elementary Shapes**** ****| Exercise 5.4**

**1. What is the measure of (a) a right angle? (b) a straight angle?**

**Answer:**

(a) 90°

(b) 180°

**2. Say True or False :**

(a) The measure of an acute angle < 90°.

(b) The measure of an obtuse angle < 90°.

(c) The measure of a reflex angle > 180°.

(d) The measure of one complete revolution = 360°.

(e) If m ∠A = 53° and m ∠B = 35°, then m ∠A > m ∠B.

**Answer:**

(a) True (b) False (c) True (d) True (e) True

**3. Write down the measures of**

**(a) some acute angles.
**

**(b) some obtuse angles.**

(give at least two examples of each).

(give at least two examples of each).

**Answer :**

(a) 50° , 75°

(b) 120°, 145°

**4. Measure the angles given below using the Protractor and write down the measure.**

**Answer:**

(a) 40°

(b) 130°

(c) 90°

(d) 60°

**5. Which angle has a large measure?**

**First estimate and then measure.**

**Measure of Angle A =**

**Measure of Angle B =**

**Answer :**

∠B has larger measure.

∠A = 40° and ∠B = 65°

**6. From these two angles which has larger measure? Estimate and then confirm by measuring them.**

**Answer:** Second angle has larger measure.

**7. Fill in the blanks with acute, obtuse, right or straight :**

**(a) An angle whose measure is less than that of a right angle is______.**

**(b) An angle whose measure is greater than that of a right angle is ______.**

**(c) An angle whose measure is the sum of the measures of two right angles is _____.**

**(d) When the sum of the measures of two angles is that of a right angle, then**

**each one of them is ______.**

**(e) When the sum of the measures of two angles is that of a straight angle and if**

**one of them is acute then the other should be _______.**

**Answer:**

(a) acute angle

(b) obtuse angle

(c) straight angle

(d) acute angle

(e) obtuse angle

**8. Find the measure of the angle shown in each figure. (First estimate with your eyes and then find the actual measure with a protractor).**

**Answer:**

(i) 30°

(ii) 120°

(iii) 60°

(iv) 150°

**9. Find the angle measure between the hands of the clock in each figure :**

**Answer:**

(i) 90° (Right angle)

(ii) 30° (Acute angle)

(iii) 180° (Straight angle)

**10. Investigate In the given figure, the angle measures 30°. Look at the same figure through a magnifying glass. Does the angle becomes larger? Does the size of the angle change?**

**Answer:** No, the measure of angle will be same.

**11. Measure and classify each angle :**

**Answer:**

Angle |
Measure |
Type |

∠AOB | 40 | Acute |

∠AOC | 130 | Obtuse |

∠BOC | 90 | Right |

∠DOC | 90 | Right |

∠DOA | 140 | Obtuse |

∠DOB | 180 | Straight |

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