If we multiply all even integers from 22 to 222, what are the last 2 digits of the product?

To solve the problem of finding the last two digits of the product of all even integers from 22 to 222, we focus on finding the product modulo 100. This is because the last two digits of any number are equivalent to that number modulo 100.

### Step 1: Identify the even integers
The even integers from 22 to 222 are:
\[
22, 24, 26, \ldots, 222
\]
This sequence is an arithmetic progression with a common difference of 2. The first term \(a_1 = 22\), and the last term \(a_n = 222\). To find the total number of terms in this sequence, we use the formula for the number of terms in an arithmetic progression:
\[
n = \frac{222 - 22}{2} + 1 = 101 \quad \text{even integers}.
\]

### Step 2: Analyze the factors of 2 and 5
To determine the last two digits, we need to consider the factors of 100, which is \(2^2 \times 5^2\). Thus, the product will be divisible by 100 if it contains at least two factors of 2 and two factors of 5.

#### Factors of 2:
All integers in the sequence are even, so each number contributes at least one factor of 2. Specifically, the multiples of 4 will contribute an additional factor of 2. Since every fourth number in the sequence is divisible by 4, the sequence will contribute many factors of 2.

#### Factors of 5:
The multiples of 5 in this sequence will contribute factors of 5. These numbers are:
\[
30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220.
\]
There are 20 numbers divisible by 5. Additionally, multiples of 10 (which are also divisible by 5) will contribute at least one factor of 5.

### Step 3: Conclusion
The product of all even integers from 22 to 222 includes more than two factors of 2 and two factors of 5, ensuring that the product is divisible by \(100 = 2^2 \times 5^2\).

Therefore, the last two digits of the product of all even integers from 22 to 222 are:
\[
\boxed{00}
\]

Would you like more details on any specific part of the solution? 

Here are 5 related questions:
1. What if we multiplied all integers (odd and even) from 22 to 222?
2. How do we count the exact number of factors of a specific prime in a product?
3. What is the significance of powers of prime factors in modulo calculations?
4. How would the result change if we wanted the last three digits instead?
5. How can we calculate large products without explicitly multiplying the numbers?

**Tip:** When dealing with the last digits of large products, breaking down the problem using prime factorization often simplifies the calculation.

If we multiply all even integers from 22 to 222, what are the last 2 digits of the product?

Learn how to find the last two digits of the product of even integers from 22 to 222 using arithmetic progression and modular arithmetic. This detailed solution covers prime factorization and factors of 100, suitable for students in Grades 9-12.

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