A Geiger-Müller detector is used to measure the radioactivity of a sample. With the sample present, the detector registers a count rate of 450 counts per minute450\text{ counts per minute}450 counts per minute. When the sample is removed, the detector registers a background radiation count rate of 30 counts per minute30\text{ counts per minute}30 counts per minute.
What is the corrected count rate of the sample?
44 exam-style questions on CIE IGCSE Physics 5.2.1 Background radiation and measuring count rate. Each one has a worked solution and a mark scheme showing where the marks go.