Two identical charges, 5 μC each, are in the air. What is the largest charge to be transferred from one charge to another, so that their interaction force decreases to 2.5 times?

GivenCharge  q=5 μCLet QμC is transferred from one charge to other.We know coloumb force F=kq2r2.....1⇒k×5×10−62r2=2.5×k5−Q5+Qr2⇒5×10−622.5=5−Q5+Q×10−12⇒25×10−122.5=25−Q2×10−12∴Q=15 μC