S. K. Gupta Anubhuti Gangal Class 5 Math Tenth Chapter Basics Of Geometry Exercise 40
EXERCISE 40
VARIOUS TYPES OF ANGLES
Acute Angle: An angle whose measure is more than 0o but less than 90o is called acute angle.
Right Angle: An angle whose measure is 90o is called right angle.
Obtuse Angle: An angle whose measure is more than 90o but less than 180o is called an obtuse angle.
Straight Angle: An angle whose measure is 180o is called a straight angle.
Reflex Angle: An angle whose measure is more than 180o but less than 360o is called a reflex angle.
Complete Angle: An angle whose measure is 360o is called a complete angle.
Zero Angle: The angle whose measure is 0o is called a zero angle.
(1) What kind of angle is shown in each figure?
(2) (a) What kind of angle is marked in the following pictures?
Ans: (i) Acute, (ii) Right, (iii) Obtuse, (iv) Reflex, (v) Acute
(b) Which of these angles are fixed, and which can change size?
Ans: (i) and, (ii) and fixed, (iii) and, (iv) can changed size.
(3) How many right-angle turns does a soldier make one after the other when he does an “about turn”.
(a) A right Angle = 90o
(5) Tell whether the angles given below are acute, right, obtuse or straight.
(a) 63o =Acute Angle
(b) 136o = Obtuse Angle
(c) 90o = Right Angle
(d) 180o = Straight Angle
(e) 101o = Obtuse Angle
(f) 89o = Acute Angle
(6) Name the number of right angles the hour hand on the clock face turns through in the direction from:
(a) 12 to 3 = 1 right angle
(b) 12 to 6 = 2 right angles
(c) 12 to 9 = 3 right angles
(d) 12 to 12 = 4 right angles
(e) 3 to 6 = 1 right angle
(f) 3 to 9 = 2 right angles
(g) 3 to 3 = 4 right angles
(h) 4 to 7 = 1 right angle
(i) 8 to 11 = 1 right angle
(7) Write 3 examples of right angles from your classroom.
(8) Can two acute angles be together to form to straight angle? Give reason for your answer.
Ans: No, because the sum of two acute angles is less than 180o.
(9) Copy the table. Use a protractor to measure each angle in the figure and complete the table.
(10) Observe the diagram drawn below and tell about each of the following angles whether it is acute, right, obtuse, or straight.
(a) ∠BAC = Acute
(b) ∠ABC = Acute
(c) ∠ACB = Obtuse
(d) ∠DCA = Acute
(e) ∠ADC = Obtuse
(f) ∠ADB = Straight
(11) Given below are all the letters of the English alphabet.
(a) List all the letters that have angles.
Ans: A, E, F, G, H, I, J, K, L, M, N, P, R, T, V, W, X, Y, Z.
(b) List all the letters that have:
(i) Acute Angles (ii) Obtuse Angles (iii) Right Angles
(i) Acute Angles = A, K, M, N, R, V, W, X, Y, Z
(ii) Obtuse Angles = A, K, Y
(iii) Right Angles = E, F, H, L, T
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