NIMCET 2007 — Reasoning PYQ
NIMCET | Reasoning | 2007The smallest number which when divided by 2, 3, 4, 5 leaves 1 as remainder in each case but, leaves no remainder when divided by 7:
Choose the correct answer:
- A.
231
- B.
301
(Correct Answer) - C.
331
- D.
none
301
Explanation
Step 1: Find the Least Common Multiple (LCM)
To find a number that is divided by 2,3,4, and 5 leaving a remainder of 1, we first need to find the smallest number completely divisible by them. This is their LCM.
Prime factorization:
2=21
3=31
4=22
5=51
LCM(2,3,4,5)=22×31×51=4×3×5=60
Step 2: Express the Required Number in General Form
Any number that leaves a remainder of 1 when divided by 2,3,4, and 5 can be written in the mathematical form:
Number=60k+1
(where k is a positive integer: k=1,2,3,…)
Step 3: Apply the Divisibility Condition for 7
The question states that the number must leave no remainder when divided by 7 (i.e., it must be perfectly divisible by 7).
Let's simplify the expression 60k+1 by breaking down 60 into a multiple of 7:
60k+1=(56k+4k)+1=56k+(4k+1)
Since 56k is always perfectly divisible by 7, we only need to find the smallest value of k for which (4k+1) is divisible by 7.
For k=1: 4(1)+1=5 (Not divisible by 7)
For k=2: 4(2)+1=9 (Not divisible by 7)
For k=3: 4(3)+1=13 (Not divisible by 7)
For k=4: 4(4)+1=17 (Not divisible by 7)
For k=5: 4(5)+1=21 (Divisible by 7 because 21÷7=3)
Step 4: Calculate the Smallest Number
Substitute k=5 back into our general form equation:
Number=60(5)+1
Number=300+1=301

