The Tropic of Cancer is the longitude that divides India into two equal parts. This is because of the following reasons:

Geographical location
- The Tropic of Cancer is located at 23.5°N latitude.
- India is located between 8°4' and 37°6' N latitude.
- This means that India is situated above the Tropic of Cancer.

Significance of Tropic of Cancer
- The Tropic of Cancer is one of the five major circles of latitude that mark maps of the Earth.
- It is the northernmost point at which the sun appears directly overhead during the summer solstice.
- This makes it a significant landmark for geography and astronomy.

Division of India
- Since India is located above the Tropic of Cancer, it can be divided into two equal parts by drawing a line along this latitude.
- This line would pass through the middle of India, dividing it into a northern and southern half.

Other longitudes
- The Prime Meridian is the line of longitude that passes through Greenwich, London and is used as a reference point for calculating time differences around the world.
- The Standard Meridian of India is the longitude that passes through the center of India and is used as the reference point for calculating Indian Standard Time (IST).
- However, neither of these longitudes divides India into two equal parts.

In conclusion, the Tropic of Cancer is the longitude that divides India into two equal parts, due to its geographical location and significance in astronomy.

In the latitude the tropic cancer divides India into two parts as it passes approximately in between the northern most point(Siachen glacier ) and the southern most point (Indira point). In the longitudinal manner the standard meridian of India 82°30' N divides India into two parts.