In a simplified model, the main sequence lifetime is proportional to the mass of usable fuel divided by the rate at which this fuel is used. Star Q has 12 times as much usable fuel as star P and uses fuel at 600 times the rate. Which statement is correct?
Q lasts 505050 times as long as P because its fuel supply dominates.
Q lasts 720072007200 times as long as P because its fuel supply dominates.
Q lasts 17200\frac{1}{7200}72001 as long as P because its fuel use dominates.
Q lasts 150\frac{1}{50}501 as long as P because its fuel use dominates.
75 exam-style questions on Edexcel GCSE Physics 7.3 Stars, covering 7.3.1 Evolution of stars similar to the Sun, 7.3.2 Evolution of massive stars, and 7.3.3 Observing the Universe. Each one has a worked solution and a mark scheme showing where the marks go.