The number of elements known in Mendeleev's presented periodic table is:

Explanation

To solve the question regarding the number of elements known in Mendeleev's presented periodic table, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: Mendeleev's periodic table was developed in the late 19th century and was a significant advancement in the classification of elements. It was based on atomic mass and chemical properties.

2. **Historical Background**: Before Mendeleev's work, other classification systems, such as Newland's octave law, were proposed but had limitations. Mendeleev's table improved upon these by organizing elements in a way that highlighted periodic trends.

3. **Identify the Number of Elements**: At the time Mendeleev created his periodic table, only a limited number of elements had been discovered. Historical records indicate that there were 63 known elements during his time.

4. **Conclude the Answer**: Therefore, the number of elements known in Mendeleev's presented periodic table is 63.

### Final Answer:
The number of elements known in Mendeleev's presented periodic table is **63**.

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