The H.C.F. of two numbers is 23 and the other two factors of their L.C.M. are 13 and 14. The larger of the two numbers is
Aptitude
HCF and LCM
Difficulty: Easy
Choose an option
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A276
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B299
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C322
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D345
Answer
Correct Answer: 322
Explanation
### Concept & Logic
When two numbers have an H.C.F. of $H$, the numbers can be represented as $Hx$ and $Hy$, where $x$ and $y$ are co-prime factors. The L.C.M. of these numbers is given by:
$$ \text{L.C.M.} = H \times x \times y $$
The problem explicitly provides $H$ and the other two factors ($x$ and $y$).
### Step-by-Step Solution
* **Given:** H.C.F. = 23, and the other two factors of the L.C.M. are 13 and 14.
* **Calculation / Deduction:** Let the two numbers be $N_1$ and $N_2$.
* Based on the concept, the numbers are $23 \times 13$ and $23 \times 14$.
* The problem asks for the larger of the two numbers.
* Larger number = $23 \times 14$.
* $23 \times 14 = 322$.
### Exam Strategy & Shortcut
You don't need to calculate both numbers. Simply identify the larger factor (14) and multiply it by the H.C.F. (23). To quickly calculate $23 \times 14$, use the unit digit trick: $3 \times 4 = 12$, so the answer must end in 2. Looking at the options, only (c) 322 ends in 2, making it an instant pick.
### Common Pitfall
A common mistake is multiplying all three numbers together ($23 \times 13 \times 14$) assuming the question asks for the L.C.M., or mistakenly assuming 13 and 14 are the numbers themselves rather than the co-prime factors. Read the prompt carefully.
### Final Answer
Therefore, the correct answer is **322**.