A 240 V parallel circuit is has 40 amps flowing through it. What is the total resistance
of the circuit?

4.80Ω

Explanation :

Voltage of circuit V = 240 volts

Total Resistance R = ?

Current, I = 40 Amp

Now recall that:

Voltage = current x resistance

i.e V = I x R

240 volts = 50Amps x R

R = (240 volts/50 Amps)

R = 4.80Ω

Thus, the total resistance of the circuit is 4.80Ω

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form