A laboratory centrifuge extracts rare-earth minerals from a solution. The mass of mineral extracted per batch, MMM grams, is modelled by a normal distribution with mean 828282 and standard deviation 6.56.56.5.
Find the probability that a randomly selected batch yields a mass greater than 959595 grams.
The extraction settings are modified, changing the mean to μ\muμ grams while keeping the standard deviation at 6.56.56.5 grams. Two independent batches are processed using these settings.
The probability that the mass extracted in both batches exceeds 909090 grams is 0.02250.02250.0225.
Find the value of μ\muμ, giving your answer to 1 decimal place.
In a separate test phase, the calibration is adjusted so that the mass extracted follows a normal distribution with mean 151515 and standard deviation 252525. Four independent batches are then processed.
Find the probability that at least one of these batches yields a negative mass reading.
Practise Edexcel A Level Maths Finding Probabilities for Normal Distributions with exam-style questions for A Level Maths. 80 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
