math
posted by christine .
Electrical system are governed by Ohm's law, which states that V = IR, where V=voltate, I=current, and R=resistance. If the current in an electrical system is decreasing at a rate of 9 A/s while the voltage remains constant at 14 V, at what rate is the resistance increasing when the current is 40 A?

so IR = 14
so when I = 40
R = 14/40 = 7/20
d(I)/dt(R) + d(R)/dt(I) = 0
9(7/20) + d(R)/dt (40) = 0
d(R)/dt = 63/20 /40
= 63/800 resistance units/s