**Understanding Elementary Shapes Class 6 Ex. 5.4 **

**New Ncert Class 6 Math Free Solution.**

**Exercise 5.4**

**Question 1 :- What is the measure of :**

**(i) a right angle **

**(ii) a straight angle?**

**Solution 1:- **

(i) Measure of a right angle = 90°

(ii) Measure of a straight angle is 180 degree.

**Question 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.**

**Solution 2:-**

(a) True

(b) False

(c) True

(d) True

(e) True

**Question 3 :- Write down the measures of**

**(a) some acute angles**

**(b) some obtuse angles**

**(give at least two examples of each).**

**Solution 3:-**

(a) 23°, 89° are acute angles.

(b) 91°, 179° are obtuse angles.

**Question 4 :- Measure the angles given below using the protractor and write down the measure.**

(a) (b)

**Solution 4:-**

(a) 45°

(b) 125°

(c) 90°

(d) ∠1 = 60°, ∠2 = 90°, ∠3 = 125°

**Question 5 :- Which angle has a large measure? First estimate and then measure.**

**Measure of Angle A =**

**Measure of Angle B =**

**Solution 5:-**

Measure of Angle A = 40°

Measure of Angle B = 60°.

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

(a) (b)

**Solution 6:-**

Angle (b)’s opening is larger than that of angle (a).

Measure of angle (a) = 45°

Measure of angle (b) = 60°

**Question 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 …………….. .**

**Solution 7:- **

(a) acute

(b) obtuse (if the angle is less than 180 degree)

(c) straight

(d) acute

(e) obtuse

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

**Solution 8:-**

(a) Measure of the angle = 40°

(b) Measure of the angle = 130°

(c) Measure of the angle = 65°

(d) Measure of the angle = 135°.

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

**Solution 9:-**

1.) At 9:00 a.m., a clock’s hour hand and minute hand make a 90° angle.

2.) At 1:00 p.m., a clock’s hour hand and minute hand make a 30° angle.

3.) At 6:00 p.m., a clock’s hour hand and minute hand make a 180° angle.

**Question 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?**

**Solution 10:-**

The angle measurement will remain unchanged when seen with a magnifying glass.

**Question 11:- Measure and classify each angle:**

**Solution 11:-**

- ∠AOB = 40 degree (acute angle).
- ∠AOC = 125 degree (obtuse angle)
- ∠BOC = 85 degree (acute angle)
- ∠DOC = 95 degree (obtuse angle)
- ∠DOA = 140 degree (obtuse angle)
- ∠DOB = 180 degree (straight angle)

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