b. It depends on the value you assume for the power line voltage. If you assume it is 120 volts, then the ratio to battery voltage is
... (120 volts)/(1.2 volts) = 100
Power line voltage is 100 times as large as battery voltage.
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Please be aware of some difficulties in this question.
1. Power line voltage, even if it is "120 volts" varies over time from -170 V to +170 V, so is not really comparable to a battery's voltage, which is steady at 1.2 V.
2. The terminology "times larger" is ambiguous. When we answer the question, "how much larger is a than b," we give the response in terms of the difference a-b. Thus, if a is 2 times larger than b, we might be talking about the difference being twice the value of b. It is preferable to say "times as large as."