UPSC CSE · CSAT · Reasoning and judgment · TOPIC LESSON
Choose among feasible alternatives using explicit priorities, rather than an attractive result that violates the rules.
BY THE END, YOU CAN
BEFORE YOU START
Original educational lesson. Work through the examples before revealing the practice answers. This original common-core lesson supports its declared paper scope. Optional subjects, qualifying language papers and the interview are outside this resource.
LEARN THROUGH ORIGINAL PRACTICE
All teaching examples, cases, prompts and model answers are original. Official exam questions and answer keys are not reproduced. This common-core lesson does not imply complete historical paper coverage or an official score.
01 / UNDERSTAND & APPLY
A decision problem specifies an actor, an action and a goal. “Improve service” is too vague until the relevant outcome and scope are identified: reduce waiting, deliver more water, protect safety or allocate a limited trial fairly. Check who may decide and what they are authorized to change.
Separate hard constraints from preferences. A safety requirement or fixed budget may exclude an option altogether. A preference for lower cost can instead be weighed against another benefit if the decision rule permits that tradeoff. Do not silently convert a hard limit into a negotiable score.
Before choosing, rewrite the task as: choose one feasible option that best satisfies the stated criterion. If no priority is supplied and alternatives trade advantages, explain what additional judgment is needed rather than inventing a personal ranking.
ORIGINAL PRACTICE · 1
A is feasible; B is not.
Benefit does not override the hard budget cap. If both exceeded the cap, the correct response would be to report no feasible option rather than choose the smaller violation without authorization.
02 / UNDERSTAND & APPLY
Make a feasibility pass before comparing benefits. Check cost, time, capacity, access and any stated safety conditions for each alternative. A plan that satisfies four out of five mandatory requirements can still be infeasible.
Use totals and compatible units. A per-trip price must be multiplied by the number of trips; a continuous two-hour task cannot fit two separated one-hour windows unless splitting is explicitly allowed. Include shared resource conflicts rather than assuming two tasks can use the same vehicle at once.
Feasibility can depend on unknown data. An unverified travel time is not zero and not automatically favourable. State the missing quantity and whether the decision can be deferred, made conditionally or escalated under the problem’s rules.
ORIGINAL WORKED EXAMPLE
Choose one water-transport plan. Cost must not exceed 1200 units and completion time must not exceed 4 hours. Among feasible plans, maximize delivered volume; if volumes tie, choose lower cost. P costs 1100, takes 5 hours and delivers 900 L. Q costs 1000, takes 4 hours and delivers 800 L. R costs 1300, takes 3 hours and delivers 1000 L. S costs 1200, takes 4 hours and delivers 950 L. Which plan wins?
Answer Choose S. Its higher cost than Q does not defeat the explicitly primary volume objective, and its cost still meets the hard cap.
ORIGINAL PRACTICE · 1
No.
The total available time is two hours, but no continuous two-hour interval exists. Adding separated periods ignores the task’s continuity constraint.
ORIGINAL PRACTICE · 2
360 units, so the stated trip cost fits the budget.
The relevant total is 3×120, not the price of one trip. This establishes only this cost condition; other unspecified constraints must not be assumed satisfied.
03 / UNDERSTAND & APPLY
A lexicographic rule ranks criteria: compare the primary one first, and use the next only when the earlier criterion ties. The water example prioritizes volume, then cost. A weighted score instead allows tradeoffs, but only when the weights, scoring direction and scales are supplied.
For an explicit example, suppose accessible options U and V are scored from 0 to 10 on reliability and convenience, higher being better. The supplied rule is 0.7×reliability+0.3×convenience. U scores 8 and 5, giving 5.6+1.5=7.1. V scores 6 and 9, giving 4.2+2.7=6.9. U wins under these stated weights even though V is more convenient.
The score is a consequence of the chosen model, not a universal fact that U is better. Different legitimate weights could change the ranking. Do not add hours to currency or invent equal weights without a stated normalization and decision rule. Hard safety conditions should still be checked before scoring if the task defines them that way.
ORIGINAL WORKED EXAMPLE
A repair decision first excludes any option failing a stated safety check, then minimizes downtime among the remaining options. Option A passes and requires 2 hours, B passes and requires 3 hours, and C fails but requires 1 hour. Which option should be selected?
Answer Select A. It passes the required check and has the shortest downtime among the safe options.
ORIGINAL PRACTICE · 1
The verified urgent case.
Arrival time is secondary and applies within tied urgency levels. The answer depends on urgency being established under the stated rule, not merely claimed by someone requesting preference.
04 / UNDERSTAND & APPLY
Option A dominates B when A is no worse on every relevant criterion and strictly better on at least one, after feasibility is checked. If A is cheaper but B is faster, neither dominates solely on those two criteria. You need an explicit priority or tradeoff judgment.
Dominance is always relative to the relevant criteria and their directions. Lower cost and waiting time may be preferred, while higher access or reliability is preferred. Omitting a material quality difference can create a false dominance claim.
ORIGINAL WORKED EXAMPLE
Three accessible staffing options fit a 100-unit budget. A costs 80 and produces a stated wait of 20 minutes; B costs 90 with a 15-minute wait; C costs 90 with a 25-minute wait. Quality is equal, and lower cost and lower wait are preferred. Which options are dominated? Can A or B be uniquely chosen without another priority?
Answer C is dominated. A and B remain incomparable without a stated priority, willingness to trade cost for time, or another relevant criterion.
ORIGINAL PRACTICE · 1
A dominates B.
A is strictly better on both relevant criteria. This conclusion would need reconsideration if a further relevant quality or access difference were introduced.
05 / UNDERSTAND & APPLY
Missing information differs from a known zero, a known failure and a known average. If a route’s travel time is unknown, a plan cannot be certified to meet a tight deadline by assigning it a favourable value. Identify which observation or verification would most affect feasibility.
A worst-case safeguard and an average-outcome preference solve different problems. Under a strict guarantee requirement, an option with travel time between 2 and 5 hours does not guarantee a 4-hour deadline. Under an explicitly stated expected-time rule, the expected value may matter, but a range alone does not supply its probabilities or mean.
Conditional planning is sometimes appropriate: choose A if a necessary check passes, otherwise use B. State who verifies the check and when the fallback activates. Do not present a conditional plan as an already verified outcome.
ORIGINAL PRACTICE · 1
No. Verify it or state the decision’s dependence on it.
Zero is a value, not a placeholder for ignorance. Assigning it could turn an infeasible plan into an apparently feasible one. A conservative bound or authorized fallback may be useful if the scenario supplies it.
06 / UNDERSTAND & APPLY
A decision can satisfy a numerical objective yet violate the actor’s authority or a stated fairness condition. Check who can authorize a disclosure, waive a requirement or choose an exception. Being helpful does not justify making up powers that the scenario does not grant.
Transparent criteria help relevantly similar cases receive comparable treatment. This does not require identical treatment where a relevant difference such as verified urgency exists. Explain the criterion, not a personal preference or status-based favour. Privacy also limits how much case information should be revealed while giving reasons.
ORIGINAL WORKED EXAMPLE
A desk may disclose a person’s appointment status only after the caller passes a stated verification procedure. An unverified caller asks whether that person has an appointment. Staff may guide the caller through verification and escalate unresolved cases to a supervisor. What response fits the constraints?
Answer Guide the caller through verification and withhold the status until authorized. The response preserves an available service route without violating the stated privacy condition.
ORIGINAL PRACTICE · 1
Explain the actual process and available next steps, and refer decisions to the authorized person.
A reassuring promise would create unsupported certainty and exceed the role. Accuracy about the process can still be helpful; uncertainty should not be concealed by an invented commitment.
07 / UNDERSTAND & APPLY
After selecting an option, identify the responsible action, essential check and fallback. A paper decision that no one implements does not deliver its intended benefit. Monitoring should address the reason the option was chosen and the risks identified, rather than collect unrelated data.
A reversible pilot can reduce uncertainty while limiting exposure, but reversibility does not remove every harm. State what is being tested, who is affected, what safeguards apply and the conditions for changing course. A trial is not a license to ignore the same authority and fairness constraints governing the original choice.
ORIGINAL WORKED EXAMPLE
Two sites meet every supplied eligibility condition for a reversible service trial. Capacity allows only one site this month. The published tie-break is the earliest complete application; Site M completed its application before Site N. The trial offers an online channel and an assisted desk. Its access safeguard requires that every verified eligible user can complete the service through at least one of those channels. A verified case where an eligible user cannot complete it through either channel triggers review by the responsible supervisor, who may modify or suspend the trial. What should be done?
Answer Select M using the published tie-break, communicate the trial’s access safeguard and monitor both channels. A verified eligible user excluded from both channels triggers supervisor review; it does not automatically prescribe one particular remedy.
ORIGINAL PRACTICE · 1
Resolve the safety check before optional cosmetic comparison.
The safety condition can exclude the option entirely, making the cosmetic comparison irrelevant. This ordering follows the given hard constraint, not a general claim that every small uncertainty requires stopping all work.
08 / UNDERSTAND & APPLY
A complete explanation says which options were feasible, which criterion decided among them, and what fact would change the result. In the water example, S wins because 950 L exceeds 800 L within both caps; lowering the budget below 1200 would change feasibility and potentially the selection.
Avoid describing a choice as universally best when it is best only under supplied priorities. If no option dominates and no priority is stated, report the unresolved tradeoff. That is more accurate than quietly importing your own weights.
These original scenarios develop constrained problem-solving. They are not official answer keys or guarantees about future question formats. The transferable skill is making assumptions, comparisons and role limits explicit enough that another reader can inspect the decision.
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