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Norrie is watching the aircraft warning lights on the tops of some tall buildings in the city. He sees two lights flash at the same time, then one of them flashes every 4th second, and the other flashes every 5th second.
How many times do they flash together during a whole minute?
Norrie then watches a third light. He sees it flash at the same time as the other two, then it flashes every 7th second. How many minutes will it be before this light flashes again at exactly the same time as the other two?
Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?
Investigate the different shaped bracelets you could make from 18 different spherical beads. How do they compare if you use 24 beads?
How many different shaped boxes can you design for 36 sweets in one layer? Can you arrange the sweets so that no sweets of the same colour are next to each other in any direction?