Question Analysis:
We are given that X atoms of A combine with Y atoms of B to form 5 molecules of a compound containing A and D. We need to find the molecular weight of the compound formed.

Given:
- X atoms of A
- Y atoms of B
- 5 molecules of the compound

To Find:
- Molecular weight of the compound formed

Solution:
To find the molecular weight of the compound formed, we first need to determine the molecular formula of the compound. Let's analyze the given information step by step.

Step 1: Combining X atoms of A with Y atoms of B
When X atoms of A combine with Y atoms of B, they form a compound containing A and D. Let's represent the molecular formula of the compound as AD.

Step 2: Determining the number of atoms of A and D in the compound
Since X atoms of A combine with Y atoms of B to form 5 molecules of the compound, we can set up the following equation:
X + Y = 5

Since each molecule of the compound contains one atom of A and one atom of D, we can write another equation:
1A + 1D = 5

Simplifying the equation, we get:
X + Y = 5
X = Y

This means that X and Y are both equal to 2.5. However, atoms cannot exist in fractions, so let's assume X = 3 and Y = 2.

Step 3: Determining the molecular formula
With X = 3 and Y = 2, we can determine the molecular formula of the compound:
AD3B2

Step 4: Calculating the molecular weight
To calculate the molecular weight of the compound, we need to know the atomic weight of B (given as M). Since the compound contains 3 atoms of A, 2 atoms of B, and 1 atom of D, the molecular weight can be calculated as follows:
Molecular weight = (3 * atomic weight of A) + (2 * atomic weight of B) + (1 * atomic weight of D)

This calculation will give us the molecular weight of the compound formed.

Summary:
The molecular weight of the compound formed by combining X atoms of A with Y atoms of B to form 5 molecules of a compound containing A and D is calculated using the molecular formula AD3B2. The molecular weight is determined by the atomic weights of A, B, and D, which can be used in the equation (3 * atomic weight of A) + (2 * atomic weight of B) + (1 * atomic weight of D).