Directions: Each question below consists of a number. Your task is to follow the following steps in order to find the result from the given alternatives. Step I: Multiply the number by 3 and add the square of the number. Step II: Divide the result obtained after Step I by 5 and add 6. Step III: Divide the result obtained after Step II by 3 and then square the resulting number. 2.5
Aptitude
Simplification
Difficulty: Medium
Choose an option
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A8.10
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B8.51 (approx.)
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C18.05
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D80.50 (approx.)
Answer
Correct Answer: 8.51 (approx.)
Explanation
### Concept & Logic
This problem requires following a predefined mathematical algorithm strictly sequentially. When dealing with decimals, converting to fractions often helps maintain precision through intermediate steps.
### Step-by-Step Solution
* **Given Input:** $x = 2.5$. It is often easier to use the fraction form $x = \frac{5}{2}$.
* **Step I: Multiply the number by 3 and add the square of the number.**
$$\text{Result}_1 = 3(2.5) + (2.5)^2$$
$$\text{Result}_1 = 7.5 + 6.25 = 13.75$$
* **Step II: Divide the result obtained after Step I by 5 and add 6.**
$$\text{Result}_2 = \frac{13.75}{5} + 6$$
$$\text{Result}_2 = 2.75 + 6 = 8.75$$
* **Step III: Divide the result obtained after Step II by 3 and then square the resulting number.**
$$\text{Result}_3 = \left( \frac{8.75}{3} \right)^2$$
Convert $8.75$ to a fraction to make squaring easier: $8.75 = \frac{35}{4}$.
$$\text{Result}_3 = \left( \frac{\frac{35}{4}}{3} \right)^2 = \left( \frac{35}{12} \right)^2$$
$$\text{Result}_3 = \frac{1225}{144}$$
Perform the final division:
$$1225 \div 144 \approx 8.5069$$
Rounding to two decimal places gives $8.51$.
### Exam Strategy & Shortcut
Avoid heavy fraction squaring by using smart decimal estimation at Step 3.
$\frac{8.75}{3}$ is slightly less than 3 (since $\frac{9}{3} = 3$).
Let's approximate it: $8.75 \div 3 \approx 2.916$.
Since $3^2 = 9$, the answer must be slightly less than 9.
Looking at the options, 8.10 is too low (that would require $2.84^2$), making 8.51 the only logical approximation.
### Common Pitfall
Struggling with the decimal division in Step II ($13.75 \div 5$). A quick trick for dividing any number by 5 is to double the number and divide by 10. $13.75 \times 2 = 27.5$. $27.5 \div 10 = 2.75$.
### Final Answer
**Therefore, the correct answer is 8.51 (approx.).**