is solution correct?

Question

ithis is not for me, im doing it for my cousin. The answer i got is 67.5 minutes. i just want some confirmation if this is correct.

question:
A fully charged cell phone can work in a standby position (you don’t talk on the phone) for 72 hours, or we can talk continually for 3 hours on it, and then we have to recharge it again. This cell phone, after it was fully charged, was on standby for 27 hours and then the owner conducted a 45 min. conversation. How many more minutes could we still talk on this phone?

p.s. ill post how i got my solution later if this question is bugging you and you want to know how i got 67.5 minutes

awsome, ok i dont need anymore answers. solution confirmed

Answer 1

Let's see.

In standby mode, each hour uses up 1/72 of the battery life.
In talk mode, each hour uses up 1/3 of the battery life.

After 27 hours of standby, you have used up 27/72 (= 3/8) of the battery life. You have also used 3/4 x 1/3 = 1/4 of the battery life for talking.

Adding these together we have used 3/8 + 1/4 = 5/8 of the battery.

This leaves 3/8 of the battery life.

Let the remaining talk time in hours be X.

(1/3)X = 3/8
X = 3/8 * 3/1
X = 9/8

That's 1 1/8 hour. Converting to minutes we have:
9/8 x 60 = 540/8 = 270/4 = 135/2 = 67.5 minutes

I agree!

Answer 2

Proportion of stand by to talk is 72 : 3 = 24 : 1.

72 - 27 gives 45 hours stand by or 45/24 hours talk= 1hr 52.5mins

1hr 52.5 - 45 mins = 67.5 mins talk time left.

Answer 3

I agree with your answer.
the ratio of talk to standby is 3:72 or 1:24
so after 27 hours of standby there are
45 hours of standby left.
therefore you could talk (45)*(1/24) hours
which is 1.875 hours
take away the 45min. (.75 hr) that you did talk
and you get 1.125 hr which is 67.5 minutes
~~

Answer 4

24 hrs of standby or 60min. you talk
7. 5 min for 3 hours of standby

67.5 min plus 45

112.5 min

3 hrs = 180 min.

180- 112.5 = 67.5 CORRECT!! YAY

Answer 5

yea its rite (: