Ada plans to bring a camera for a trip and expects to spend more than 6 hours in taking photos for the whole trip.
camera is powered by 2 batteries of the same type
lifetime of alkaline operating is 20 min
lifetime of chargeable operating is 100 min
if she will bring only 10 batteries, at most how many alkaline batteries can she bring
inequalities?
2016-02-11 12:39 pm
回答 (1)
2016-02-11 1:37 pm
Let n be the number of alkaline batteries.
Then, the number of chargeable batteries = 10 - n
Time of operation more than 6 hours (6 × 60 minutes).
20n + 100(10 - n) > 6 × 60
20n + 1000 - 100n > 360
1000 - 80n > 360
1000 - 80n - 1000 > 360 - 1000
-80n > -640
80n < 640
n < 8
n is an integer.
Number of alkaline batteries that she can bring = 7
Then, the number of chargeable batteries = 10 - n
Time of operation more than 6 hours (6 × 60 minutes).
20n + 100(10 - n) > 6 × 60
20n + 1000 - 100n > 360
1000 - 80n > 360
1000 - 80n - 1000 > 360 - 1000
-80n > -640
80n < 640
n < 8
n is an integer.
Number of alkaline batteries that she can bring = 7
收錄日期: 2021-04-18 14:28:33
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