Chapter 5 Understanding Elementary Shape Ex 5.4 Solutions
Question - 1 : - What is the measure of
(i) a right angle?
(ii) a straight angle
Answer - 1 : -
(i) The measure of aright angle is 900
(ii) The measure of astraight angle is 1800
Question - 2 : - Say True or False:
(a) The measure of an acute angle < 900
(b) The measure of an obtuse angle < 900
(c) The measure of a reflex angle > 1800
(d) The measure of one complete revolution = 3600
(e) If m ∠A = 530 and m ∠B = 350, then m ∠A > m ∠B.
Answer - 2 : -
(a) True, the measure ofan acute angle is less than 900
(b) False, the measureof an obtuse angle is more than 900 but less than 1800
(c) True, the measureof a reflex angle is more than 1800
(d) True, the measureof one complete revolution is 3600
(e) True, ∠A is greater than ∠B
Question - 3 : - Write down the measures of
(a) some acute angles
(b) some obtuse angles
(give at least two examples of each)
Answer - 3 : -
(a) The measures of anacute angle are 500, 650
(b) The measures ofobtuse angle are 1100, 1750
Question - 4 : - Measures the angles given below using the protractor and write down themeasure.
Answer - 4 : -
(a) The measure of anangle is 450
(b) The measure of anangle is 1200
(c) The measure of anangle is 900
(d) The measures of anangles are 600, 900 and 1300
Question - 5 : - Which angle has a large measure? First estimate and then measure.
Measure of Angle A =
Measure of Angle B =
Answer - 5 : -
The measure of angle Ais 400
The measure of angle Bis 680
∠B has a large measurethan ∠A
Question - 6 : - From these two angles which has largermeasure? Estimate and then confirm by measuring them.
Answer - 6 : -
The measures of theseangles are 450 and 550. Hence, angle shown in secondfigure is greater.
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 anglesis _______
(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 straightangle and if one of them is acute then the other should be ______
Answer - 7 : -
(a) An angle whose measureis less than that of a right angle is acute angle
(b) An angle whosemeasure is greater than that of a right angle is obtuse angle (but less than1800)
(c) An angle whosemeasure is the sum of the measures of two right angles is straight angle
(d) When the sum ofthe measures of two angles is that of a right angle, then each one of them isacute angle
(e) When the sum ofthe measures of two angles is that of a straight angle and if one of them isacute then the other should be obtuse angle.
Question - 8 : - Find the measure of the angle shown in each figure. (First estimate withyour eyes and then find the actual measure with a protractor).
Answer - 8 : -
The measures of theangles shown in above figure are 400, 1300, 650 and1350
Question - 9 : - Find the angle measure between the hands of the clock in each figure:
Answer - 9 : -
The angle measurebetween the hands of the clock are 900, 300 and 1800
Question - 10 : - In the given figure, the angle measure 300. Look at the samefigure through a magnifying glass. Does the angle becomes larger? Does the sizeof the angle change?
Answer - 10 : -
The measure of anangle will not change by viewing through a magnifying glass