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A fully charged cellular phone can work in a standby positions (which means that we do not use it for making phone calls) for 72 hours, or we can talk continuously for 3 hours on it, and then we ahve to recharge it again. This cell phone, after t was fully charged, was in standby position for 27 hours, and the owner conducted a 45-minute conversation, also. How many more minutes could we talk on this phone?

 Dec 22, 2021
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Let B be the fully charged battery capacity.

Talking continuously for 1 hour drains B/3 capacity.

Standby for 1 hour drains B/72 capacity.

 

The standby has drained 27 * B/72 = 3B/8 capacity. 

The conversation drained B/3 * 45/60 = B/4 capacity.

In total, we've drained (3/8 + 1/4) = 5/8 B capacity.

We can talk for 3/8 B more capacity.

How many hours worth is 3/8 B on conversation mode?

B/hr = 3

3B/8hr = 3*3/8 = 9/8 hr.

9/8 hr = 67.5 min

 Dec 22, 2021

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