NCERT Solutions Ganita Prakash Chapter 2 Figure it Out — The Unlabelled Protractor
Book page 35 Updated on2026-09-05
Q1.
Write the measures of the following angles: a. ∠KAL b. ∠WAL c. ∠TAK. (Notice that the vertex of this angle coincides with the centre of the protractor. So the number of units of 1 degree angle between KA and AL gives the measure of ∠KAL. By counting, we get ∠KAL = 30°. Making use of the medium sized and large sized marks, is it possible to count the number of units in 5s or 10s?)
Answer
The unlabelled protractor of page 35. Counting the long (10°) marks gives ∠KAL = 30°, ∠WAL = 50° and ∠TAK = 120°.
Count the 1° units between the two arms. The long marks come after every 10° and the medium marks after every 5°, so you can count in tens and fives instead of one by one.
Angle
How to count
Measure
a. ∠KAL
3 long marks = 3 × 10
30°
b. ∠WAL
5 long marks = 5 × 10
50°
c. ∠TAK
12 long marks = 12 × 10
120°
Yes, counting in 5s and 10s is definitely possible — and it is far quicker and safer than counting 120 single marks.
Check it yourself: measured on the printed page the three rays sit at 30.5°, 52.4° and 120.3° from one another — exactly the 30°, 50° and 120° that careful counting gives.
Why the marks are of three sizes: long marks every 10°, medium marks every 5° and short marks every 1°. They act like the big and small divisions on a ruler, so the eye can jump ten at a time and then adjust.