_______ is a type of scale on which three successive dimensions can be measured.
- AEngineer's scale
- BVernier scale
- CDiagonal scaleCorrect
- DScale of chords
Solution
Concept
A diagonal scale reads three successive units, such as m, dm and cm.
Step-by-step solution
1. A plain scale reads only two units, for example m and dm. 2. A diagonal scale uses diagonal lines to divide the smallest division again. 3. So it reads three units, for example m, dm and cm. 4. The answer is the diagonal scale.
Explanation
A diagonal scale works on the principle of similar triangles. It divides a short length into many equal parts. This lets us read three successive dimensions, such as metre, decimetre and centimetre.
Why the other options are wrong
A: An engineer's scale is a common measuring scale, not a special three-unit scale. B: A vernier scale gives fine readings using two scales (main and vernier), not three units. D: A scale of chords is used to measure or set out angles.
Shortcut
Plain scale = 2 units, Diagonal scale = 3 units.
Common mistake
Choosing the vernier scale because it also gives fine readings.
Correct answer: C) Diagonal scale