Math Problem Statement

1x2x3x4x5x6x...x206x207x208 + 3 divided by 30, what is the remaining number?

Solution

The given expression is:

(1×2×3×4××208)+330\frac{(1 \times 2 \times 3 \times 4 \times \cdots \times 208) + 3}{30}

First, notice that 1×2×3××2081 \times 2 \times 3 \times \cdots \times 208 represents the factorial of 208, denoted as 208!208!. So, the expression becomes:

208!+330\frac{208! + 3}{30}

Now, we are interested in the remainder when 208!+3208! + 3 is divided by 30.

Step 1: Analyze 208!208! modulo 30

We know that 208!208! is the product of all integers from 1 to 208. Since 208!208! includes multiples of 2, 3, and 5 (which are factors of 30), it follows that 208!208! is divisible by 30. Therefore:

208!mod30=0208! \mod 30 = 0

Step 2: Consider 208!+3208! + 3 modulo 30

Since 208!0mod30208! \equiv 0 \mod 30, we can now calculate:

(208!+3)mod30=(0+3)mod30=3(208! + 3) \mod 30 = (0 + 3) \mod 30 = 3

Thus, the remainder when (208!+3)(208! + 3) is divided by 30 is 3.

Final Answer:

The remainder is 3.

Would you like any additional details or clarification?

Here are 5 related questions to consider:

  1. What is the definition of factorial and how is it used in combinatorics?
  2. How do you calculate large factorials efficiently?
  3. How do modular arithmetic and remainders work in division problems?
  4. What are the properties of divisibility rules for numbers like 30?
  5. What role do prime factors play in simplifying large factorials?

Tip: For large numbers, breaking the problem into smaller parts, such as focusing on the factors of the divisor, simplifies the process.

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Math Problem Analysis

Mathematical Concepts

Factorials
Modular Arithmetic
Divisibility

Formulas

n! = n × (n - 1) × (n - 2) × ... × 1
Modular Arithmetic: (a + b) mod n = ((a mod n) + (b mod n)) mod n

Theorems

Factorial Divisibility by 30: Factorials involving multiples of 2, 3, and 5 are divisible by 30
Modular Arithmetic Theorem

Suitable Grade Level

Grades 10-12