Voltmeter sensitivity (ohm per volt ratings)
The sensitivity of a voltmeter is given in ohms per volt. It is determined by dividing the sum of the resistance of the meter (Rm) plus the series resistance (Rs), by the full-scale reading in volts. In equation form, sensitivity is expressed as follows:
Sensitivity (S) = (Rm + Rs) ⁄ Vfld
Now as per the given question
Rm= 400 KΩ
Rs = 100 KΩ
Vfld= 250 V
S = (400 + 100) ⁄ 250
S = (500 × 103) ⁄ 250
S = 2000 ohm/volt