I have a RC circuit that has R=1MΩ and C=1μF. I need to figure out how long will it take for Vc to reach 90V. I'm using the formula t=2.3*RC*log V/v. The answer I get is 1.2s but my book says 356.7ms. What am I doing wrong?

Vc -> Condensator voltage V -> Input voltage t -> time source: http://en.wikipedia.org/wiki/RC_circuit hope that help

Hmm T=-RC*In(Vin-Vc)/Vin=1s*In(210/300)=-1s*In0.7=-1s*-0.356.67m=356.67mS http://www.allaboutcircuits.com/vol_1/chpt_16/8.html