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Vaccines have become an effective way to prevent certain diseases, however for some viruses it is difficult to develop a vaccine. Describe possible difficulties of developing a permanent vaccine for the influenza virus.

The influenza virus has a very high mutation rate. This means that its surface proteins (antigens) will change. Since a vaccine contains a specific antigen, if the virus switches to a different antigen, then...
NL
Answered by Nancy L. • Biology tutor
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Explain the stages of the cardiac cycle

The cardiac cycle consists of series of chamber systole and diastole. Systole is the name given to a period when cardiac muscle contract to cause blood ejection from the respective chamber to another. Diasto...
AB
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Paul organised an event for a charity. Each ticket for the event cost £19.95 Paul sold 395 tickets. Paul paid costs of £6000 He gave all money left to the charity. (a) Work out an estimate for the amount of money Paul gave to the charity.

This question asks us to estimate the amount of money Paul gave to Charity. To work out an estimate we must start by rounding the numbers we are given to 1 significant figure and the Starting with 19.95 --&g...
PP
Answered by Priti P. • Maths tutor
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Amy earns £6 for every hour she works Monday to Friday. She earns £8 for every hour she works on Saturday. One week Amy worked for 5 hours on Saturday - she earned £130 that week. How many hours did she work from Monday to Friday?

Amy worked for 5 hours on Saturday so she earned £8 x 5 = £40 on that day. She earned £130 in total so we know she earned £130 - £40 = £90 working from Monday to Friday. For every hour Amy worked from Monday...
HM
Answered by Hamza M. • Maths tutor
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A cylinder has a circular face with a diameter of 10cm, and a body of length 30cm. Calculate the volume of the cylinder.

First recognise that the diameter is 10cm so the radius of the circle must be 5cm. Next use the formula for the area of a circle, πr 2 , to work out the area of the circular face: Area = 25πcm 2 Multiply thi...
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Answered by Hamza M. • Maths tutor
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