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Maths · Grade 4 · Set C
Protractor, then think
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C
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Goal: 15 min
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Remember: Read the mark where the second ray crosses, starting at zero. A right angle is 90 degrees and a straight line is 180 degrees.

Read it carefully

1
The baseline lies along zero. How many degrees is the angle?
2
Read the protractor. How many degrees is this angle?
3
Read the protractor. How many degrees is this angle?
50 degrees130 degrees40 degrees
4
Max says this angle is 40 degrees. What is his mistake?
There is no mistake.He forgot to add the baseline.He counted from the wrong end. The angle starts at zero, so it is 140 degrees.

Use the readings

5
The ray shows how many degrees are already open. How many more degrees make it a right angle?
6
A straight line is 180 degrees. The ray shows how many degrees are open. How many more degrees reach the straight line?
7
Three angles are put side by side. How many degrees in all?
8
A 70 degree angle and a 110 degree angle put side by side make a straight line.
TrueFalse
9
Pip opens a door 50 degrees and then 40 degrees more. The door is now open as a right angle.
TrueFalse
10
Two rays cross the scale at 30 and at 100. How many degrees is the angle between the two rays?
11
Put the angles in order from the smallest to the biggest.
  • a right angle
  • a 150 degree angle
  • a 20 degree angle
  • a 60 degree angle
12
Draw an angle that measures 70 degrees. Then write whether it is acute, right or obtuse.
13
Write how you know 70 degrees and 110 degrees make a straight line.
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Answer key · Set C
Protractor, then think
1100 The ray crosses the mark just past 90, which is 100. It is a little wider than a right angle.
2170 The ray is two small marks past 150, and each small mark is 10. So it is 170 degrees.
3130 degrees Start at zero on the baseline. The ray is one small mark past 120, so it is 130. 50 is how far the ray is from the other end.
4He counted from the wrong end. The angle starts at zero, so it is 140 degrees. The baseline is along zero. The ray is two small marks past 120, so the angle is 140 degrees. It is obtuse, not acute.
530 A right angle is 90 degrees. The angle is 60 degrees, and 90 − 60 = 30.
670 180 − 110 = 70 degrees.
7150 30 + 50 = 80, and 80 + 70 = 150 degrees.
8True 70 + 110 = 180, and a straight line is 180 degrees.
9True 50 + 40 = 90, and a right angle is 90 degrees.
1070 Count the steps from 30 to 100: 100 − 30 = 70 degrees.
113, 4, 1, 2 A right angle is 90 degrees. In order: 20, 60, 90, 150.
13Your own words: a grown-up reads it.
Mark each answer, count the right ones and write the score on the sheet.