The countries like usa and russia have adopted more than one standard time why?

Both USA and Russia are huge countries in size and if they have only one standard time then the difference between the real time and standard time of two ends would be very large so to avoid this, these countries have two standard times.

The countries like USA and Russia have adopted more than one standard time because

these countries are too large and the difference in latitude between the corners of these countries will also be large which wont be proper.

The time should be almost same in all the places in order to select a standard time , therefore to keep the time accurate at its cities or places they have  adopted more than one standard time 

answer:

The countries like USA and Russia have adopted more than one standard time due to their great longitudinal extent.

Explanation:

The local time of different locations have different meridian values. Therefore, it is essential to embrace the local time of some country's central meridian as the normal uniformity time for the nation. In India, 82°C (82°30'E) longitude is regarded as the normal meridian and the local time at that meridian is deemed the standard time for the entire nation. It is referred to as the Indian Standard Time (IST). Similarly, owing to their large longitudinal extent, some nations have embraced more than one standard time. There are as many as eleven normal times in Russia, for instance. The earth was split into twenty-four one-hour time zones.

This is because as the the area they cover is so big and the longitudes pass through them are more than one so they have more than one standard time.