Answer:
1 ohm
Explanation:
since there are two identical resistors, one resistor will be
R =
=2ohm [ proven as in series
]
to calculate the equivalent resistance when in parallel:

so,


I'm pretty sure it is true. (78% sure)
1) 72/4 = 18 years
2) 72/10 = 7.2 years
3) 72/13 = 5.54 years
Explanation: With the rule of 72, you simply take 72 and divide it by whatever the rate of return (or return on investment) is.
Let me know if you have any questions.