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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)...

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 highlighte...

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 ...

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 'pacemake...

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...