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Let x be the least number which when div...

Let x be the least number which when divided by 8, 9, 12, 14 and 36 leaves a remainder of 4 in each case, but x is divisible by 11. The sum of the digits of x is .........

A

5

B

6

C

9

D

4

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the least number \( x \) that meets the following criteria: 1. When divided by 8, 9, 12, 14, and 36, it leaves a remainder of 4. 2. It is divisible by 11. ### Step 1: Find the LCM of the divisors We first need to find the least common multiple (LCM) of the numbers 8, 9, 12, 14, and 36. - **Prime factorization**: - \( 8 = 2^3 \) - \( 9 = 3^2 \) - \( 12 = 2^2 \times 3^1 \) - \( 14 = 2^1 \times 7^1 \) - \( 36 = 2^2 \times 3^2 \) - **LCM calculation**: - Take the highest power of each prime: - For 2: \( 2^3 \) - For 3: \( 3^2 \) - For 7: \( 7^1 \) Thus, the LCM is: \[ \text{LCM} = 2^3 \times 3^2 \times 7^1 = 8 \times 9 \times 7 = 504 \] ### Step 2: Formulate the equation for \( x \) Since \( x \) leaves a remainder of 4 when divided by 8, 9, 12, 14, and 36, we can express \( x \) as: \[ x = 504k + 4 \] for some integer \( k \). ### Step 3: Ensure \( x \) is divisible by 11 We need \( x \) to be divisible by 11: \[ 504k + 4 \equiv 0 \mod{11} \] First, calculate \( 504 \mod 11 \): \[ 504 \div 11 = 45 \quad \text{(integer part)} \] \[ 504 - (45 \times 11) = 504 - 495 = 9 \] Thus, \( 504 \equiv 9 \mod{11} \). Now, substitute this back into our equation: \[ 9k + 4 \equiv 0 \mod{11} \] This simplifies to: \[ 9k \equiv -4 \mod{11} \] Since \(-4 \equiv 7 \mod{11}\), we have: \[ 9k \equiv 7 \mod{11} \] ### Step 4: Solve for \( k \) To solve for \( k \), we can test integer values: - For \( k = 1 \): \[ 9 \times 1 \equiv 9 \mod{11} \quad \text{(not a solution)} \] - For \( k = 2 \): \[ 9 \times 2 \equiv 18 \equiv 7 \mod{11} \quad \text{(solution found)} \] ### Step 5: Calculate \( x \) Now substitute \( k = 2 \) back into the equation for \( x \): \[ x = 504 \times 2 + 4 = 1008 + 4 = 1012 \] ### Step 6: Find the sum of the digits of \( x \) Now, we need to find the sum of the digits of \( 1012 \): \[ 1 + 0 + 1 + 2 = 4 \] ### Final Answer The sum of the digits of \( x \) is **4**.
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