What is the third term in a sequence of numbers that leave remainders of $1$, $2$ and $3$ when divided by $2$, $3$ and $4$ respectively?
Aptitude
HCF and LCM
Difficulty: Medium
Choose an option
-
A11
-
B17
-
C19
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D35
Answer
Correct Answer: 35
Explanation
### Concept & Logic
The remainders are $1, 2, 3$ for divisors $2, 3, 4$.
Notice the difference between Divisor and Remainder is constant:
$2-1 = 1$, $3-2 = 1$, $4-3 = 1$.
The general number is $N = \text{LCM}(2, 3, 4)k - 1$.
### Step-by-Step Solution
* **Find LCM:**
$\text{LCM}(2, 3, 4) = 12$.
* **Formulate sequence:**
$N = 12k - 1$.
* **Find terms:**
For $k=1$, $N = 12(1) - 1 = 11$ (First term).
For $k=2$, $N = 12(2) - 1 = 23$ (Second term).
For $k=3$, $N = 12(3) - 1 = 35$ (Third term).
### Exam Strategy & Shortcut
Once you find the first term ($11$) and the LCM ($12$), the subsequent terms in the sequence are just an arithmetic progression:
$11, 11+12=23, 23+12=35$.
### Common Pitfall
Confusing the sequence with a simple $+1$ pattern. Always calculate the LCM of the divisors to determine the common difference for the sequence.
### Final Answer
**Therefore, the correct answer is 35.**