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For a vernier calliper where 1 main scale division (MSD) = 1 mm and 7 MSD = 8 vernier scale divisions (VSD), and with no zero error, a rod is measured to have length 4(x/8) mm. Find the value of x.

1. 0
2. 4
3. 8
4. 12

Correct answer: 4

Solution

Least count = 1 MSD - 1 VSD = 1 - 7/8 = 1/8 mm. If the main scale reads 4 mm and the nth vernier division coincides, length = 4 + n/8 mm = (32 + n)/8 mm. The expression 4(x/8) = 4x/8 = x/2. Setting (32+n)/8 = 4x/8... this question is figure-dependent for the coinciding division. Given the option x = 4 (length = 4*4/8 = 2 mm) doesn't seem right. Most likely x represents the coinciding vernier division, and the answer is 4 (the 4th vernier line coincides).

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