Question Details

Find the least number which when divided by 5, 6, 3 and 4 leaves a remainder 2, but when divided by 7 leaves no remainder.2660

Options

A

168

B

147

C

198

D

182

Show Answer

Correct Answer :

Option D

182

Solution :

The correct option is 182.


To find the least number that leaves a remainder of 2 when divided by 5, 6, 3, and 4, but is completely divisible by 7 (leaves no remainder), we follow these step-by-step logical reasoning and mathematical steps:

Step 1: Find the Least Common Multiple (LCM) of the divisors (5, 6, 3, and 4).
First, let's find the prime factorization of each number:
• 5 = 51
• 6 = 21 × 31
• 3 = 31
• 4 = 22

The LCM is obtained by taking the highest power of each prime factor involved:
LCM(5,6,3,4)=22×31×51=4×3×5=60

Step 2: Formulate the general expression for the required number.
Any number that leaves a remainder of 2 when divided by 5, 6, 3, and 4 must be of the form:
Required Number=60k+2
where k is a positive integer (k=1,2,3,...).

Step 3: Find the value of k such that 60k+2 is divisible by 7.
We can rewrite 60 in terms of multiples of 7:
60=7×8+4

So, the expression becomes:
60k+2=(56k+4k)+2=56k+(4k+2)

Since 56k is always divisible by 7 (as 56 = 7 × 8), the entire number 60k+2 will be divisible by 7 if and only if (4k+2) is divisible by 7.

Now, test integer values for k starting from 1:
• For k=1: 4(1)+2=6 (not divisible by 7)
• For k=2: 4(2)+2=10 (not divisible by 7)
• For k=3: 4(3)+2=14 (which is completely divisible by 7, as 14 = 7 × 2)

Step 4: Calculate the required number.
Substitute k=3 back into the general expression:
Required Number=60(3)+2=180+2=182

Thus, the least number satisfying all the given conditions is 182.

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