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505-555 Level|   Word Problems|         
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Kimberly77
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The temperature of a certain cup of coffee 10 minutes after it was pou 22 Oct 2022, 12:05
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Crystal clear now thanks Bunuel. So it's 3 steps in the between. Have a good weekend.
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The temperature of a certain cup of coffee 10 minutes after it was pou 27 Oct 2022, 06:17
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kilukilam
The temperature of a certain cup of coffee 10 minutes after it was poured was 120 degrees Fahrenheit. If the temperature F of the coffee t minutes after it was poured can be determined by the formula F = 120*2^(-at) + 60, where F is in degrees Fahrenheit and a is a constant. Then the temperature of the coffee 30 minutes after it was poured was how many degrees Fahrenheit?

A. 65
B. 75
C. 80
D. 85
E. 90

First we need to find the value of a using F = 120 and t = 10:

120 = 120 * 2^(-10a) + 60

60 = 120 * 2^(-10a)

1/2 = 2^(-10a)

2^(-1) = 2^(-10a)

With a common base, we can equate the exponents:

-1 = -10a

a = 1/10

Now we can find F using a = 1/10 and t = 30:

F = 120 * 2^(-(1/10)(30)) + 60

F = 120 * 2^(-3) + 60

F = 120 * 1/8 + 60

F = 15 + 60

F = 75

Answer: 2/B

Great explanation ScottTargetTestPrep, If we cancel out 120 at this stage, I'm not sure how to proceed next? Could you help? Thanks

120 = 120 * 2^(-10a) + 60
1 = 2^(-10a) + 60
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You cannot cancel 20 at that point because of the (+ 60) on the right hand side.
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The temperature of a certain cup of coffee 10 minutes after it was pou 27 Oct 2022, 14:09
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Great thanks ScottTargetTestPrep for the clarification. Is there a break of PEMDAS here? as I was thinking to calculation the * / first. Thanks for your time in advanced.
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The temperature of a certain cup of coffee 10 minutes after it was pou 03 Nov 2022, 18:34
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Kimberly77
Great thanks ScottTargetTestPrep for the clarification. Is there a break of PEMDAS here? as I was thinking to calculation the * / first. Thanks for your time in advanced.
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It actually does not have anything to do with PEMDAS. If you divide by 120 on the right side, you have to divide every term by 120, which includes the 60.
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The temperature of a certain cup of coffee 10 minutes after it was pou 04 Nov 2022, 10:39
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Kimberly77
Great thanks ScottTargetTestPrep for the clarification. Is there a break of PEMDAS here? as I was thinking to calculation the * / first. Thanks for your time in advanced.

It actually does not have anything to do with PEMDAS. If you divide by 120 on the right side, you have to divide every term by 120, which includes the 60.
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Great thanks ScottTargetTestPrep for great helps always. Make sense now.
This is such an easy trap to fall into of cancelling 120 out at this stage :lol: Any advice to prevent this type of silly mistake? will be very much appreciated. Thanks Scott.
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The temperature of a certain cup of coffee 10 minutes after it was pou 11 Nov 2022, 08:45
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Kimberly77
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Kimberly77
Great thanks ScottTargetTestPrep for the clarification. Is there a break of PEMDAS here? as I was thinking to calculation the * / first. Thanks for your time in advanced.

It actually does not have anything to do with PEMDAS. If you divide by 120 on the right side, you have to divide every term by 120, which includes the 60.

Great thanks ScottTargetTestPrep for great helps always. Make sense now.
This is such an easy trap to fall into of cancelling 120 out at this stage :lol: Any advice to prevent this type of silly mistake? will be very much appreciated. Thanks Scott.
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Yes! Slow WAY DOWN when practicing questions. Usually, rushing is what causes these kinds of mistakes.
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The temperature of a certain cup of coffee 10 minutes after it was pou 12 Nov 2022, 01:58
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Ok thanks ScottTargetTestPrep for the advice
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The temperature of a certain cup of coffee 10 minutes after it was pou 02 Aug 2025, 11:27
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what a sum not certainly 555 level it's higher need focous and concentration to solve it

kilukilam
The temperature of a certain cup of coffee 10 minutes after it was poured was 120 degrees Fahrenheit. If the temperature F of the coffee t minutes after it was poured can be determined by the formula \(F = 120*2^{(-at)} + 60\), where F is in degrees Fahrenheit and a is a constant. Then the temperature of the coffee 30 minutes after it was poured was how many degrees Fahrenheit?

A. 65
B. 75
C. 80
D. 85
E. 90
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