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STATEMENT -1: The tens digit of 1! + 2! ...

STATEMENT -1: The tens digit of 1! + 2! + 3! + 4! + 5! +........... + 50! is 1.
STATEMENT-2 : The sum of divisors of `2^(4)3^(5)5^(2)7^(3)` is `2^(5).3^(6).5^(3).7^(4) - 2.3.5.7.`

A

(a)Statement-1 is true ,statement -2 is true , statement -2 is a correct explanation for statement -3

B

(b)Statement -1 is true , statement -2 is true , statement -2 is NOT a correct explanation for statement -3

C

(c)Statement -1 is true , statement -2 is false

D

(d)Statement -1 is false , statement -2 is true

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze both statements separately. ### Statement 1: The tens digit of \(1! + 2! + 3! + 4! + 5! + \ldots + 50!\) is 1. 1. **Calculate Factorials**: - \(1! = 1\) - \(2! = 2\) - \(3! = 6\) - \(4! = 24\) - \(5! = 120\) - \(6! = 720\) - For \(n \geq 10\), \(n!\) will end with at least two zeros (because \(10! = 3628800\) and higher factorials will have more trailing zeros). 2. **Sum of Factorials**: - We only need to consider the factorials from \(1!\) to \(9!\) since \(10!\) and above contribute \(0\) to the tens digit. - Calculate the sum: \[ 1 + 2 + 6 + 24 + 120 + 720 + 5040 + 40320 + 362880 \] - Adding these values: - \(1 + 2 = 3\) - \(3 + 6 = 9\) - \(9 + 24 = 33\) - \(33 + 120 = 153\) - \(153 + 720 = 873\) - \(873 + 5040 = 5913\) - \(5913 + 40320 = 46233\) - \(46233 + 362880 = 409113\) 3. **Identify the Tens Digit**: - The total sum is \(409113\). - The tens digit is \(1\). Thus, **Statement 1 is true**. ### Statement 2: The sum of divisors of \(2^4 \cdot 3^5 \cdot 5^2 \cdot 7^3\) is \(2^5 \cdot 3^6 \cdot 5^3 \cdot 7^4 - 2 \cdot 3 \cdot 5 \cdot 7\). 1. **Calculate the Sum of Divisors**: - The formula for the sum of divisors \( \sigma(n) \) for \( n = p_1^{k_1} \cdot p_2^{k_2} \cdots p_m^{k_m} \) is: \[ \sigma(n) = (1 + p_1 + p_1^2 + \ldots + p_1^{k_1})(1 + p_2 + \ldots + p_2^{k_2}) \cdots (1 + p_m + \ldots + p_m^{k_m}) \] - For \(2^4\): \[ 1 + 2 + 4 + 8 + 16 = 31 \] - For \(3^5\): \[ 1 + 3 + 9 + 27 + 81 + 243 = 364 \] - For \(5^2\): \[ 1 + 5 + 25 = 31 \] - For \(7^3\): \[ 1 + 7 + 49 + 343 = 400 \] 2. **Combine the Results**: - Now, multiply these sums: \[ 31 \cdot 364 \cdot 31 \cdot 400 \] 3. **Simplifying Statement 2**: - The statement claims that this product equals \(2^5 \cdot 3^6 \cdot 5^3 \cdot 7^4 - 2 \cdot 3 \cdot 5 \cdot 7\). - We need to check if the left-hand side equals the right-hand side. 4. **Conclusion**: - After performing the calculations, we find that the left-hand side does not equal the right-hand side. - Therefore, **Statement 2 is false**. ### Final Conclusion: - **Statement 1 is true** and **Statement 2 is false**. Thus, the correct option is **C**.
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