0, but there are 2 commas if thats what you mean
It is now accepted in the UK that a billion is 1,000,000,000 (one thousand million), (it used to be 1,000,000,000,000 ie, one million million). We use the comma, though I believe the period is used in the USA? Therefore, where I've shown a comma, simply assume it is a period if you are in the USA!
3 periods
11,530,000.0 Note the use of commas and fullstops/periods.
None.
There is actually none.
45,000,000,000,000,000,million years
0, but there are 2 commas if thats what you mean
many periods
Million
They are both time periods of the early Paleozoic. The Ordovician was approximately 490 million years ago, to 440 million years ago. The Silurian was approximately 440 million years ago, to 416 million years ago. The Silurian was the period immediately after the Ordovician. The two periods were divided by the second largest Mass extinction in history.
There have been multiple glacial periods during the last two million years, with Earth experiencing numerous advances and retreats of ice sheets. This period is commonly referred to as the Quaternary Ice Age, characterized by alternating cold glacials and warmer interglacial periods.
About 250 million years, from 300m to 65m, spanning three periods(Triassic, Jurassic, and Cretaceous
There have been multiple glacial periods, known as ice ages, during the last two million years. These ice ages are characterized by intervals of cold climate when ice sheets covered much of the Earth's surface. The exact number of glacial periods can vary depending on the scientific definition used.
The Ice Age.
The Mesozoic Era occured approximately 252 to 66 million years ago. It is divided into three periods: the Triassic, Jurassic, and Cretaceous periods. This era is known for the dominance of dinosaurs and the rise of mammals and flowering plants.
The Cenozoic era has three periods. These periods include the Paleogene, the Neogene, and Quaternary. This era covers a span of 66 million years ago until present time.