1) consider resis. 2 be 10 ohms each..balance pt. at 50 cm

   when increased by 10% the left becomes 11 and right resistor remains 10 ohms..

 

now balanced pt is 11/21 * 100 = 52.4 approx

 

increase = (2.4 * 100)/50 = 4.8% to the right