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A cup of coffee is cooling down in a room following the equation x = 15 + 70e^(-t/40). Find the rate at which the temperature is decreasing when the coffee cools to 60°C.

First, we need to find the value of t when x = 6p°C. We are told that after t minutes the temperature, x, will be 60°C; so we can insert 60 into the equation for x: 60 = 15 + 70e^(-t/40) Secondly, we can rea...
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Answered by Nathan A. • Maths tutor
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How do you revise for an English Literature exam?

Ah yes, the question which haunted my years of study, particularly during GCSE and A Levels. At this stage, many exams are ‘open book’ - that is, you can take either a blank or highlighted copy of the text i...
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What is the difference between oxidation and reduction?

In chemistry if a substance is oxidised it loses electrons in a reaction. If a substance is reduced it gains electrons in a reaction. A reaction that has both oxidation and reduction within it is called a RE...
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Answered by Thomas C. • Chemistry tutor
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What are the events in the cardiac cycle?

The cardiac cycle is the series of events that leads to blood being pumped to the lungs and around the body. The cycle begins with the SAN (sino-atrial node). This is the hearts 'pacemaker'. It sends out a n...
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Answered by Thomas C. • Biology tutor
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How do white blood cells protect us from infection?

Sometimes microorganisms are able to make it past the body's external defences (i.e. the skin) the body's immune system must defend the body. White blood cells are really important in the immune response. Th...
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Answered by Thomas C. • Biology tutor
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