Quantitative Aptitude – Caselets
(AWS Certification Preparation – Quantitative Aptitude)
1. What is a “Caselet”?
A caselet is a short, real‑world problem that blends qualitative reasoning with quantitative calculations.
- Length: 5–10 minutes (usually 2–3 sentences).
- Format: Often found in the “Verbal Reasoning” or “Quantitative” sections of competitive exams, including AWS certification (e.g., AWS Certified Cloud Practitioner – Quantitative Aptitude).
Why it matters
- Tests your ability to interpret a scenario, identify relevant data, and apply the right formula/logic quickly.
- Real‑world context mirrors the problem‑solving style AWS uses in its exam questions.
2. Key Features of Caselets
| Feature | Description | Why it matters |
|---|---|---|
| Scenario‑Based | Uses a narrative (e.g., “A company has 120 servers…”) | Mimics AWS real‑world challenges |
| Multiple Variables | Usually 4–6 numbers/percentages | Requires quick mental bookkeeping |
| Hidden Assumptions | Not all data is explicitly stated | Tests inference skills |
| Single Answer | One numeric result or choice | Focus on precision |
| Time Constraint | 1–2 minutes per caselet | Builds speed |
3. Problem‑Solving Strategy (Step‑by‑Step)
-
Read the entire caselet once
Don’t get stuck on the first sentence. -
Identify the question
What is being asked? (e.g., “What will be the total cost after 3 years?”) -
Extract the data
Write down all numbers, units, and percentages. -
Understand the relationships
- Look for multiplication, division, percentage change, or compound growth.
- Convert percentages to decimals when needed.
-
Choose the appropriate formula
- Simple interest: (I = P \times r \times t)
- Compound interest: (A = P (1+r)^t)
- Percentage change: (New = Old \times (1 \pm %/100))
- Average: (\frac{Sum}{Count})
-
Do a quick sanity check
- Does the answer make sense in context?
- Is the unit correct?
-
Answer
- If it's multiple choice, eliminate wrong options swiftly.
4. Worked Example
Caselet
A cloud startup has 200 servers. 30% of them are dedicated to data analytics, and the rest are for web hosting.
Each analytics server costs $300/month, and each web server costs $200/month.
The startup plans to increase the number of analytics servers by 20% next month while keeping the total number of servers constant.
Question: What will be the new total monthly cost of all servers?
Step‑by‑Step Solution
-
Identify the question
New total monthly cost after the change. -
Extract data
- Total servers = 200
- Analytics servers = 30% of 200 = 60
- Web servers = 200 – 60 = 140
- Cost per analytics server = $300
- Cost per web server = $200
-
Compute current cost
(C_{\text{current}} = 60 \times 300 + 140 \times 200 = 18{,}000 + 28{,}000 = 46{,}000) -
Determine change
- Increase analytics servers by 20%:
(60 \times 0.20 = 12) new analytics servers. - Since total servers remain 200, we must decrease web servers by 12.
- New analytics = 60 + 12 = 72
- New web = 140 – 12 = 128
- Increase analytics servers by 20%:
-
Compute new cost
(C_{\text{new}} = 72 \times 300 + 128 \times 200)
(= 21{,}600 + 25{,}600 = 47{,}200) -
Sanity check
The cost increased by $1,200 (≈2.6 %), which is reasonable given the higher‑cost analytics servers. -
Answer
$47,200 per month.
5. Quick Revision Summary
| Concept | Quick Tip |
|---|---|
| Percentages | Convert to decimal: 20% → 0.20 |
| Increase/Decrease | (New = Old \times (1 \pm \frac{p}{100})) |
| Total Cost | Sum of (quantity × unit cost) |
| Keeping Total Constant | If one type increases, subtract the same amount from the other type |
| Time Management | Spend ≤ 45 s on data extraction, ≤ 30 s on calculation, ≤ 15 s on sanity check |
Final Note
Mastering caselets sharpens analytical thinking and quick calculations, which are essential for the AWS certification’s quantitative section. Practice with varied scenarios—cost optimization, capacity planning, and performance metrics—to build confidence and speed. Happy studying!