Light A flashes every 5 seconds.
Light B flashes every 6 seconds.
Light C flashes every 7 seconds.
All three lights flash at the same time.
Work out how long it will take for all three lights to flash at the same time again.
59 exam-style questions on Edexcel GCSE Maths Prime Factors, HCF and LCM. Each one has a worked solution and a mark scheme showing where the marks go.