Ques 1: What is the disadvantage in comparing line segments by mere observation?
Ans: There may be chance of error due to improper viewing.
Ques 2: Why is it better to use a divider than a ruler, while measuring the length of a line segment?
Ans: It is better to use a divider than a ruler, because the thickness of the ruler may cause difficulties in reading off her length. However divider gives up accurate measurement.
Ques 3: Draw any line segment, say Take any point C lying in between A and B. Measure the lengths of AB, BC and AC. Is AB = AC + CB?
[Note: If A, B, C are any three points on a line, such that AC + CB = AB, then we can be sure that C lies between A and B.]
AB = 6.5 cm, AC = 3cm, CB = 3.5 cm
AC + CB = 3 cm + 3.5 cm = 6.5 cm = AB
Ques 4: If A, B, C are three points on a line such that AB = 5 cm, BC = 3cm and AC = 8 cm, which one of them lies between the other two?
Ans: is the longest line segment, thus B is the point between A and C.
Ques 5: Verify whether D is the mid-point of .
Ans: AD = 3 units, DG = 3 units
AD = DG.
Thus, D is the mid-point.
Ques 6: If B is the mid-point of and C is the mid-point of where A, B, C, D lie on a straight line, say why AB = CD?
Ans: B is the mid-point of .
∴ AB = BC ... (i)
And C is the mid-point of .
∴ BC = CD ... (ii)
From equation (i) and (ii), we get
AB = CD
Ques 7: Draw five triangles and measure their sides. Check in each case, of the sum of the lengths of any two sides is always less than the third side.
Ans: Yes, sum of two sides of a triangle is always greater than the third side.
Ques 1: What fraction of a clockwise revolution does the hour hand of a clock turn through, when it goes from
(a) 3 to 9
(b) 4 to 7
(c) 7 to 10
(d) 12 to 9
(e) 1 to 10
(f) 6 to 3
Ans: (a) 1/2 or two right angles.
(b) 1/4 or one right angle.
(c) 1/4 or one right angle.
(d) 3/4 or three right angles.
(e) 3/4 or three right angles.
(f) 3/4 or three right angles.
Ques 2: Where will the hand of a clock stop if it:
(a) starts at 12 and make 1/2 of a revolution, clockwise?
(b) starts at 2 and makes 1/2 of a revolution, clockwise?
(c) starts at 5 and makes 1/4 of a revolution, clockwise?
(d) starts at 5 and makes 3/4 of a revolution, clockwise?
Ans: (a) At 6
(b) At 8
(c) At 8
(d) At 2
Ques 3: Which direction will you face if you start facing:
(a) East and make 1/2 of a revolution clockwise?
(b) East and make of a revolution clockwise?
(c) West and makes 3/4 of a revolution, clockwise?
(d) South and make one full revolution?
(Should we specify clockwise or anti-clockwise for this last question? Why not?)
Ans: (a) West
(For answer (d), it is immaterial whether we turn clockwise or anticlockwise, because one full revolution will bring us back to the original position)
Ques 4: What part of a revolution have you turned through if you stand facing:
(a) East and turn clockwise to face north?
(b) South and turn clockwise to face east?
(c) West and turn clockwise to face east?
Ans: (a) 3/4
Ques 5: Find the number of right angles turned through by the hour hand of a clock when it goes from:
(a) 3 to 6
(b) 2 to 8
(c) 5 to 11
(d) 10 to 1
(e) 12 to 9
(f) 12 to 6
Ans: (a) One right angle
(b) Two right angles
(c) Two right angles
(d) One right angle
(e) Three right angles
(f) Two right angles
Ques 6: How many right angles do you make if you start facing:
(a) South and turn clockwise to west?
(b) North and turn anti-clockwise to east?
(c) West and turn to west?
(d) South and turn to north?
Ans: (a) One right angle
(b) Three right angles
(c) Four right angles
(d) Two right angles
Ques 7: Where will the hour hand of a clock stop if it starts:
(a) from 6 and turns through 1 right angle?
(b) from 8 and turns through 2 right angles?
(c) from 10 and turns through 3 right angles?
(d) from 7 and turns through 2 straight angles?
Ans: (a) At 9
(b) At 2
(c) At 7
(d) At 7
Ques 1: Match the following:
|(i) Straight angle||(a) less than one-fourth a revolution|
|(ii) Right angle||(b) more than half a revolution|
|(iii) Acute angle||(c) half of a revolution|
|(iv) Obtuse angle||(d) one-fourth a revolution|
|(v) Reflex angle||[e] between 1/4 and 1/2 of a revolution|
|(f) one complete revolution|
(i) → (c)
(ii) → (d)
(iii) → (a)
(iv) → (e)
(v) → (b)
Ques 2: Classify each one of the following angles as right, straight, acute, obtuse or reflex:
Ans: (a) Acute angle
(b) Obtuse angle
(c) Right angle
(d) Reflex angle
(e) Straight angle
(f) Acute angle