Home
Class 14
MATHS
Let x be the least number of 4 digits th...

Let x be the least number of 4 digits that when divided by 2, 3, 4, 5, 6 and 7 leaves a remainder of 1 in each case. If x lies between 2000 and 2500, then what is the sum of the digits of x?

A

9

B

15

C

10

D

4

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we need to find the least number \( x \) that meets the specified conditions: 1. **Understanding the Problem**: We want to find the least four-digit number \( x \) such that when \( x \) is divided by 2, 3, 4, 5, 6, and 7, it leaves a remainder of 1. This means that \( x - 1 \) must be divisible by all these numbers. 2. **Finding the LCM**: To find \( x - 1 \), we need to calculate the least common multiple (LCM) of the numbers 2, 3, 4, 5, 6, and 7. - The prime factorization of each number is: - \( 2 = 2^1 \) - \( 3 = 3^1 \) - \( 4 = 2^2 \) - \( 5 = 5^1 \) - \( 6 = 2^1 \times 3^1 \) - \( 7 = 7^1 \) - The LCM is found by taking the highest power of each prime: - \( 2^2 \) from 4, - \( 3^1 \) from 3 or 6, - \( 5^1 \) from 5, - \( 7^1 \) from 7. - Thus, the LCM is: \[ \text{LCM} = 2^2 \times 3^1 \times 5^1 \times 7^1 = 4 \times 3 \times 5 \times 7 \] - Calculating this step by step: - \( 4 \times 3 = 12 \) - \( 12 \times 5 = 60 \) - \( 60 \times 7 = 420 \) 3. **Finding \( x \)**: Since \( x - 1 \) must be a multiple of 420, we can express \( x \) as: \[ x = 420k + 1 \] where \( k \) is a positive integer. 4. **Finding the Range**: We need \( x \) to be a four-digit number between 2000 and 2500: \[ 2000 \leq 420k + 1 \leq 2500 \] Subtracting 1 from all parts gives: \[ 1999 \leq 420k \leq 2499 \] Dividing by 420: \[ \frac{1999}{420} \leq k \leq \frac{2499}{420} \] Calculating the bounds: - \( \frac{1999}{420} \approx 4.76 \) (so \( k \geq 5 \)) - \( \frac{2499}{420} \approx 5.95 \) (so \( k \leq 5 \)) Therefore, the only integer value for \( k \) is 5. 5. **Calculating \( x \)**: Substituting \( k = 5 \): \[ x = 420 \times 5 + 1 = 2100 + 1 = 2101 \] 6. **Finding the Sum of the Digits**: The digits of 2101 are 2, 1, 0, and 1. Thus, the sum of the digits is: \[ 2 + 1 + 0 + 1 = 4 \] **Final Answer**: The sum of the digits of \( x \) is \( \boxed{4} \). ---
Promotional Banner

Similar Questions

Explore conceptually related problems

Find the least three digit number which when divided by 20, 30, 40 and 50 leaves remainder 10 in each case.

What is the largest number of 4 digits which divided by 6,9,12, 15 ,18 leaves 1 as remainder in each case

Find the greatest four - digits number which when divided by 4,7 and 13 leaves a remainder 3 in each case.