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

Let x be the least number which when divided by 12, 15, 18, 20 and 27, the remainder in each case is 2, but x is divisible by 23. If x is divided by the sum of its digits then the quotient is:

A

196

B

149

C

193

D

199

Text Solution

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The correct Answer is:
To solve the problem step by step, we need to find the least number \( x \) that meets the given conditions. ### Step 1: Find the LCM of the numbers We need to find the least common multiple (LCM) of the numbers 12, 15, 18, 20, and 27. - **Prime factorization**: - \( 12 = 2^2 \times 3^1 \) - \( 15 = 3^1 \times 5^1 \) - \( 18 = 2^1 \times 3^2 \) - \( 20 = 2^2 \times 5^1 \) - \( 27 = 3^3 \) - **LCM Calculation**: - Take the highest power of each prime: - For \( 2 \): \( 2^2 \) - For \( 3 \): \( 3^3 \) - For \( 5 \): \( 5^1 \) Thus, the LCM is: \[ LCM = 2^2 \times 3^3 \times 5^1 = 4 \times 27 \times 5 = 540 \] ### Step 2: Adjust for the remainder Since \( x \) leaves a remainder of 2 when divided by 12, 15, 18, 20, and 27, we can express \( x \) as: \[ x = 540m + 2 \] where \( m \) is a positive integer. ### Step 3: Ensure divisibility by 23 Next, we need \( x \) to be divisible by 23: \[ 540m + 2 \equiv 0 \mod 23 \] Calculating \( 540 \mod 23 \): \[ 540 \div 23 \approx 23.478 \quad \Rightarrow \quad 23 \times 23 = 529 \quad \Rightarrow \quad 540 - 529 = 11 \] So, \( 540 \equiv 11 \mod 23 \). Now we have: \[ 11m + 2 \equiv 0 \mod 23 \quad \Rightarrow \quad 11m \equiv -2 \mod 23 \quad \Rightarrow \quad 11m \equiv 21 \mod 23 \] ### Step 4: Solve for \( m \) To solve \( 11m \equiv 21 \mod 23 \), we need the multiplicative inverse of 11 modulo 23. Testing values, we find: \[ 11 \times 21 \equiv 1 \mod 23 \] Thus, the inverse is \( 21 \). Multiply both sides by 21: \[ m \equiv 21 \times 21 \mod 23 \quad \Rightarrow \quad m \equiv 441 \mod 23 \] Calculating \( 441 \mod 23 \): \[ 441 \div 23 \approx 19.173 \quad \Rightarrow \quad 23 \times 19 = 437 \quad \Rightarrow \quad 441 - 437 = 4 \] So, \( m \equiv 4 \mod 23 \). ### Step 5: Calculate \( x \) Substituting \( m = 4 \) into the equation for \( x \): \[ x = 540 \times 4 + 2 = 2160 + 2 = 2162 \] ### Step 6: Find the sum of the digits of \( x \) Now, we calculate the sum of the digits of \( 2162 \): \[ 2 + 1 + 6 + 2 = 11 \] ### Step 7: Calculate the quotient Finally, we divide \( x \) by the sum of its digits: \[ \frac{2162}{11} = 196 \] Thus, the quotient is: \[ \boxed{196} \]
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