Arsenic levels in groundwater are typically 200-500 µg/l in bangladesh. convert this range to ppb. assume 1l of water is 1 kg.

1 ppb means one part in 1 billion. It can be converted into  as follows:

Also, 1 L is equal to 1 kg because density of water is 1 kg/L.

Thus,

The arsenic level in groundwater in Bangladesh ranges from to . This can be converted into ppb as follows:

and,

Therefore, the range in ppb is 200-500 ppb.

the answer is symmetrical : )