What will come in place of the question mark (?) in the following questions ?
`sqrt((5xxsqrt1600xxsqrt((1024))))=28-:7xx?`

Options

A. 16
B. 40
C. 8
D. 20

Answer

To solve the equation \( \sqrt{5 \times \sqrt{1600} \times \sqrt{1024}} = \frac{28}{7} \times ? \), we will break it down step by step.

### Step 1: Simplify the left-hand side
Start with the left-hand side of the equation:
\[ \sqrt{5 \times \sqrt{1600} \times \sqrt{1024}} \]

### Step 2: Calculate \( \sqrt{1600} \)
\[ \sqrt{1600} = 40 \quad (\text{since } 40^2 = 1600) \]

### Step 3: Calculate \( \sqrt{1024} \)
\[ \sqrt{1024} = 32 \quad (\text{since } 32^2 = 1024) \]

### Step 4: Substitute back into the equation
Now substitute these values back into the left-hand side:
\[ \sqrt{5 \times 40 \times 32} \]

### Step 5: Calculate \( 5 \times 40 \times 32 \)
First, calculate \( 5 \times 40 \):
\[ 5 \times 40 = 200 \]
Then, calculate \( 200 \times 32 \):
\[ 200 \times 32 = 6400 \]

### Step 6: Calculate \( \sqrt{6400} \)
Now, calculate the square root:
\[ \sqrt{6400} = 80 \quad (\text{since } 80^2 = 6400) \]

### Step 7: Set up the equation
Now we have:
\[ 80 = \frac{28}{7} \times ? \]

### Step 8: Simplify \( \frac{28}{7} \)
Calculate \( \frac{28}{7} \):
\[ \frac{28}{7} = 4 \]

### Step 9: Substitute back into the equation
Now the equation becomes:
\[ 80 = 4 \times ? \]

### Step 10: Solve for ?
To find \( ? \), divide both sides by 4:
\[ ? = \frac{80}{4} = 20 \]

### Final Answer
The value that comes in place of the question mark (?) is:
\[ \boxed{20} \]