The number of trees in each row of a garden is equal to the total number of rows in the garden. After 111 trees have been uprooted in a storm, there remain 10914 trees in the garden. The number of rows of trees in the garden is
Aptitude
Square Root and Cube Root
Difficulty: Medium
Choose an option
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A100
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B105
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C115
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D125
Answer
Correct Answer: 105
Explanation
### Concept & Logic
This problem is a two-step application of algebraic modeling and square roots. We must first account for the trees lost in the storm before calculating the grid dimensions.
### Step-by-Step Solution
* Let the initial number of rows in the garden be $x$.
* Since the number of trees in each row equals the number of rows, the initial number of trees per row is also $x$.
* Original total number of trees = $x \cdot x = x^2$.
* **Given:** $111$ trees were uprooted, leaving $10914$ trees remaining.
* We can set up the equation for the original total:
* Original Total = Remaining Trees + Uprooted Trees
* $x^2 = 10914 + 111$
* $x^2 = 11025$
* Now, solve for $x$ by finding the square root:
* $x = \sqrt{11025}$
* Any number ending in $25$ has a square root ending in $5$.
* Ignore the last two digits ($25$) and look at the remaining part: $110$.
* We need to find two consecutive integers whose product is $110$. Those integers are $10$ and $11$ (since $10 \times 11 = 110$).
* Take the smaller integer ($10$) and append the $5$.
* Thus, $x = 105$.
### Exam Strategy & Shortcut
Master the shortcut for squaring numbers that end in 5. The pattern for $(n5)^2$ is to compute $n \times (n+1)$ and append $25$.
When you reach $x^2 = 11025$, you can immediately see the $25$ suffix. The prefix $110$ is clearly $10 \times 11$.
This instantly tells you the root is $105$. No manual calculation or division is required.
### Common Pitfall
A common error is setting up the equation backwards (e.g., $x^2 - 10914 = 111$), which works mathematically, but some students mistakenly subtract $111$ from $10914$ instead of adding it, finding $x^2 = 10803$ which is not a perfect square and leads to panic. Always ensure your total represents the intact original state.
### Final Answer
**Therefore, the correct answer is 105.**