Understanding Elementary Shapes
Exercise 5.4
Questions with (*) sign are open-ended questions.
1). What is the measure of (i) a right angle? (ii) a straight angle?
(i) the measure of a right angle is 900.
(ii) the measure of a straight angle is 1800.
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 reflex angle > 1800.
d). The measure of one complete revolution = 3600.
e). If m∠A = 53° and m∠B = 35°, then m∠A > m∠B 0.
Answers:
a). The measure of an acute angle < 900.
True.
b). The measure of an obtuse angle < 900.
False.
c). The measure of reflex angle > 1800.
True.
d). The measure of one complete revolution = 3600.
True.
e). If m∠A = 53° and m∠B = 35°, then m∠A > m∠B 0.
True.
3). Write down the measure of
a). some acute angles.
10, 300, 350, 450, 780 are measures of some acute angles.
b). some obtuse angles.
(give at least two examples).
910, 1300, 1050, 1450, 1780 are measures of some obtuse angles.
4). Measure the angles given below using the Protractor and write down the measure.
Answer:
5). Which angle has a large measure?
First estimate and then measure.
Measure of Angle A = 40°
Measure of Angle B = 50°
Angle B has a large measure.
6). From these two angles which has larger measure? Estimate and then confirm by measuring them.
Answer:
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 acute.
b). an angle whose measure is greater than that of a right angle is obtuse.
c). An angle whose measure is the sum of the measures of two right angles is straight angle.
d). When the sum of the measure of two angles is that of a right angle, then each one of them is acute.
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 obtuse.
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:
9). Find the angle measure between the hands of the clock in each figure:
9.00 a.m. 1.00 p.m. 6.00 p.m.
Answer:
10). Investigate
In the given figure, the angle measure 300. Look at the same figure through a magnifying glass. Does the angle becomes larger? Does the size of the angle change?
Answer:
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