If a scientists starts with 1000 atoms of radium-226, how much would remain after 3,200 years? A

1000 × 1/2 = 500

so, 500 × 1/2 = 250 atoms

Hope it helps.

that scientist would be robert hooke

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.