Almost everyone learns time and work the fraction way first: A does 1/12 of the work in a day, B does 1/18, together they do 5/36, so they finish in 36/5 days. It is correct, and under a 15-minute sectional timer it is slow, because you are adding unlike fractions in the middle of a paper. The LCM method removes that entirely. Take the total work as the LCM of the given days, turn each person into a number of units per day, and the whole chapter, including pipes and cisterns and men-women-boys problems, becomes addition and subtraction of small whole numbers. This page teaches that method and gives you real SSC questions to run it on.
Time and work belongs to the arithmetic portion of Quantitative Aptitude in CGL Tier-1, which is 25 questions for 50 marks with a 15-minute timer of its own inside the 60-minute paper, marked +2 for a correct answer and -0.50 for a wrong one. SSC names time and work in its published Quantitative Aptitude syllabus but gives no topic-wise question count, and the real count varies from shift to shift, so no honest page can quote you a fixed number. What previous-year papers do show is that time and work, along with its close relatives pipes and cisterns and time-speed-distance, is one of the arithmetic families that keeps returning, and that a question from it is usually solvable in well under a minute once the LCM method is automatic. The topic reappears at a higher standard in the mathematical abilities module of Tier-2. Check the official notification for this cycle's dates.
If A finishes in 12 days and B in 18, set the total work at 36 units. A does 3 units a day, B does 2, together 5, so they finish in 36/5 = 7.2 days. Nothing here needs a common denominator, and the same 36 units survive every twist the question adds afterwards. Our practice sets start you on two-person problems and escalate to three-person and leaving-work variants while keeping the same first step, so the habit forms rather than the formula.
If A is twice as efficient as B, A takes half the time; if the ratio of their times is 3:4, the ratio of their efficiencies is 4:3. Half the men-women-boys questions in SSC papers are only this inversion dressed up in a story. Once you convert every stated time into an efficiency before doing anything else, questions such as "6 men and 8 women do in 10 days what 26 men and 48 women do in 2 days" become a pair of simple linear relations instead of a wall of text.
An inlet pipe is positive units per hour and a leak is negative units per hour, and that is genuinely the whole difference. Taking the tank as the LCM of the filling and emptying times lets you handle a tank filled by two pipes and drained by a third without a single fraction. The Quant AI tutor will work through the tricky variants with you, in Hindi or English, including the ones where a pipe is opened late or closed early.
The variants that cost marks are rarely the plain ones: A and B working on alternate days, A leaving three days before completion, or a group joined midway. These need a clean cycle-by-cycle count, and errors in them look like carelessness while actually being conceptual. Our post-mock AI sorts every mistake into conceptual, calculation, careless or time-pressure and builds a seven-day plan from what it finds, so if the alternate-day variant is your blind spot it comes back to you deliberately instead of by chance.
Instead of treating one day's work as a fraction, you take the total work as the LCM of all the given completion times, which makes every worker's daily output a whole number of units. If A takes 10 days and B takes 15, set total work at 30 units, so A does 3 units a day and B does 2. Combined work, work left, and a worker joining or leaving then become simple addition and subtraction. It is the single biggest speed gain available in this chapter and it works for pipes and cisterns without modification.
Work out the combined output of one full two-day cycle first, then see how many complete cycles fit inside the total work, and handle the remainder separately. Using LCM units keeps this clean: if the total is 36 units and a cycle produces 5 units, seven cycles cover 35 units in 14 days and the last unit takes a fraction of the fifteenth day. Watch who starts, because the answer changes when the faster worker begins, and SSC does ask both versions of the same numbers.
Efficiency and time taken are inversely proportional for the same quantity of work. If the ratio of efficiencies of A and B is 5:3, the ratio of the times they take alone is 3:5. This single relation resolves most questions phrased as "A is 25% more efficient than B" or "A takes 8 days less than B", because converting the comparison into a ratio of times gives you the equation directly. Practising a set of questions that only differ in how the comparison is worded makes the conversion automatic.
Structurally they are the same chapter. A filling pipe contributes positive units per hour, an emptying pipe or a leak contributes negative units, and the tank's capacity plays the role of total work. The only genuinely different variants are the ones where a pipe is opened or closed partway through, which need you to track the timeline rather than just the rates. If you are comfortable with time and work in LCM units, you already know most of pipes and cisterns.
Practise it under the clock, not in a comfortable untimed set, because the topic's whole value is that it is fast once the method is automatic. Use real previous-year questions: about 29,000 of the roughly 31,000 questions in our bank are genuine previous-year SSC questions with the Commission's own official answer keys, so you see SSC's actual phrasing rather than a coaching imitation. Then put it back in context with the free full mock test, which mirrors CGL Tier-1 with 100 questions, four sections of 25 and 15-minute sectional locks, and let the AI analysis tell you whether your errors are conceptual or simply rushed.
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