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.
16 exam-style questions on CIE IGCSE Maths Prime Factors, HCF and LCM. Each one has a worked solution and a mark scheme showing where the marks go.