Introduction:
When formaldehyde (CH2O) reacts with ammonia (NH3), a condensation reaction takes place, resulting in the formation of hexamethylene tetramine (C6H12N4). Hexamethylene tetramine is a cyclic compound consisting of a six-membered ring with alternating carbon and nitrogen atoms.

Explanation:
To determine the number of six-membered rings in hexamethylene tetramine, we need to analyze its molecular structure.

Step 1: Molecular Formula:
The molecular formula of hexamethylene tetramine is C6H12N4. This formula tells us that the compound contains 6 carbon atoms, 12 hydrogen atoms, and 4 nitrogen atoms.

Step 2: Structural Formula:
The structural formula of hexamethylene tetramine can be represented as:

H H H H H H
| | | | | |
H - C - C - C - C - C - N
| | | | |
N N N N

In the structural formula, the carbon atoms are represented by 'C', nitrogen atoms by 'N', and hydrogen atoms by 'H'. The lines connecting the atoms represent chemical bonds.

Step 3: Identifying Rings:
To count the number of six-membered rings, we need to identify all the possible rings in the structure. In hexamethylene tetramine, there are four six-membered rings formed by the carbon and nitrogen atoms. These rings can be visualized as follows:

N H H H H H
| | | | | |
H - C - C - C - C - C - N
| | | | |
N H H H H H

N H H H H H
| | | | | |
H - C - C - C - C - C - N
| | | | |
N H H H H H

N H H H H H
| | | | | |
H - C - C - C - C - C - N
| | | | |
N H H H H H

N H H H H H
| | | | | |
H - C - C - C - C - C - N
| | | | |
N H H H H H

Conclusion:
Based on the molecular structure of hexamethylene tetramine, we can observe that there are four six-membered rings present in the compound. These rings contribute to the overall structure and properties of hexamethylene tetramine.