SME
Grade 4 Math · Problem type
Measure angles: neither ray on zero
Use this for “One ray points to 45 and the other to 135. What is the angle?”
Diagram
Neither arm is on 0.
The arms read 45 and 135 on the inner scale: 135 − 45 = 90°.
Angle: 90°
This is an example. Type your own values to start a new problem.
Second arm reads
°
−
First arm reads
°
=
Angle
°
Formulas
135 − 45 = 90
Second arm reads − first arm reads = angle
Assumptions
•
Read both arms on the same scale of the protractor.
•
The angle is the difference between the two readings.
•
Readings from 0° to 180°.
Step-by-step
WE KNOW
First arm reads: 45°
Second arm reads: 135°
FIND
angle
Step 1 · Find angle
135 − 45 = ?
Second arm reads − first arm reads = angle
Take the smaller reading from the bigger one.
0
13
1
3
5
−
4
5
9
0
Angle = 90°
Check
Put the numbers back in. Both sides should match.
135 − 45 = 90 ✓
Topic check
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