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3 years ago

A light bulb consumes 960 watt-hours per day. How many watt-hours does it consume in 3 days and 18 hours?

Mathematics

2 answers:

oksano4ka [1.4K]3 years ago

7 0

960 x 3 = 2880

18/24 = 0.75

960x 0.75 = 720

2880 + 720 = 3600

Pie3 years ago

4 0

Okay. Let's explain this. 960 per day. So let's start simple: 3 days and 960 per day is basically 2880 total watt-hours. Then we must do the 18 hours. How? We must multiply it the same way we did with the whole days. So we recognize that 18 hours is 18/24 hours in a day which is simplified: 18/24, 9/12, 3/4. So basically 18 hours is 3/4 of a day. So then we must multiply it by 3/4 of 960. So 960 x 3 = 2880, 2880 / 4 = 720. So then we must add them all up: 2880 + 720 = 3600 watt-hours in 3 days and 18 hours.

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Solve for x:
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Sub back into original cooling equation, x = T(t)
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$60 (\frac{11}{30})^{t/3} +9(\frac{11}{30})^{\frac{-10}{3}}(\frac{11}{30})^{t/3} = 60 \\ \\ (\frac{11}{30})^{t/3} = \frac{60}{60+9(\frac{11}{30})^{\frac{-10}{3}}} \\ \\ \\ t = 3(\frac{ln(\frac{60}{60+9(\frac{11}{30})^{\frac{-10}{3}}})}{ln (\frac{11}{30})}) \\ \\ \\ t = 4.959$

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