Practice Questions
Concept Explanation
Time-and-work DS problems test whether worker rates or total work can be determined from given statements.
Standard Answer Choices
- A — Statement I alone is sufficient; Statement II alone is not.
- B — Statement II alone is sufficient; Statement I alone is not.
- C — Both together are sufficient, neither alone.
- D — Either statement alone is sufficient.
- E — Neither alone nor together is sufficient.
Time/Work DS Focus
Work = Rate × Time. If A finishes in x days, daily rate = 1/x of the job.
DS Decision Flow
- State exactly what must be determined (number, ratio, yes/no, or comparison).
- Test Statement I alone—sufficient or insufficient?
- Test Statement II alone—sufficient or insufficient?
- If neither alone works, combine both statements.
- Choose A–E based on sufficiency; never pick a value when data do not fix it uniquely.
Common Traps in Time/Work Problems
- Adding days instead of adding rates.
- Ignoring whether workers work simultaneously or alternately.
- Assuming equal efficiency without statement support.
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Q1 EasyA completes a job in 10 days. In 5 days he completes:ExplanationRate = 1/10 per day; in 5 days = 5/10 = 1/2. Hence the answer is 1/2 of job.
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Q2 EasyB finishes work in 15 days. Daily part of job is:ExplanationRate = 1/15 per day. Hence the answer is 1/15.
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Q3 EasyFor “Combined time?” — I: A takes 10 days; II: B takes 15 days. DS answer?ExplanationNeed both individual times: 1/10 + 1/15 = 1/6 ⇒ 6 days. Hence the answer is C.
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Q4 EasyA does twice the work of B in the same time. Ratio of efficiencies A : B is:ExplanationTwice the work ⇒ twice the rate. Hence the answer is 2 : 1.
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Q5 EasyFor “How long do A and B take together?” — I: A alone takes 10 days; II: B alone takes 15 days. Which DS option (A–E) applies?ExplanationCombined rate needs both individual times: 6 days. Hence the answer is C.
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Q6 MediumFor “Days for 8 workers?” — I: 6 workers take 12 days; II: total work is fixed. DS answer?ExplanationMan-days = 72; 8 workers ⇒ 9 days. II alone does not give days without worker count. Hence the answer is A.
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Q7 MediumA (10 days) and B (15 days) together finish in:ExplanationCombined rate = 1/10 + 1/15 = 1/6; time = 6 days. Hence the answer is 6 days.
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Q8 Medium12 men finish a job in 8 days. 16 men finish in:ExplanationMan-days = 96; 96/16 = 6 days. Hence the answer is 6 days.
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Q9 MediumFor “How many days does A alone take to finish the job?” — I: A and B together finish in 6 days; II: B alone finishes in 15 days. Which DS option (A–E) applies?Explanation1/A + 1/15 = 1/6 ⇒ A = 10 days. Need both statements. Hence the answer is C.
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Q10 MediumA works 4 days and completes 2/5 of a job. Whole job takes A:Explanation4 days = 2/5 ⇒ full job = 10 days. Hence the answer is 10 days.
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Q11 MediumFor “How many days will 8 workers take?” — I: 6 workers finish the job in 12 days; II: All workers have the same efficiency. Which DS option (A–E) applies?ExplanationMan-days = 72; 8 workers ⇒ 9 days. Statement II alone lacks worker count. Hence the answer is A.
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Q12 MediumThree equal workers finish in 9 days. One worker finishes in:ExplanationTotal man-days = 27; one worker = 27 days. Hence the answer is 27 days.
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Q13 HardFor “How long for A alone?” — I: A and B together take 6 days; II: B alone takes 15 days. DS answer?Explanation1/A + 1/15 = 1/6 ⇒ 1/A = 1/10 ⇒ A = 10 days. Need both. Hence the answer is C.
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Q14 HardPipe A fills tank in 6 hrs; B empties in 12 hrs. Together net fill time is:ExplanationNet rate = 1/6 − 1/12 = 1/12; time = 12 hrs. Hence the answer is 12 hrs.
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DS1 Easy
How long do A and B take together?
Statement IA alone takes 10 days.
Statement IIB alone takes 15 days.
ExplanationCombined rate needs both individual times: 6 days. Answer: C. -
DS2 Easy
How many days does A alone take?
Statement IA completes half the job in 5 days.
Statement IIB alone takes 20 days.
ExplanationStatement I: full job = 10 days. Statement II does not give A’s time. Answer: A.
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DS3 Medium
How many days does A alone take to finish the job?
Statement IA and B together finish in 6 days.
Statement IIB alone finishes in 15 days.
Explanation1/A + 1/15 = 1/6 ⇒ A = 10 days. Need both statements. Answer: C. -
DS4 Medium
How many days will 8 workers take?
Statement I6 workers finish the job in 12 days.
Statement IIAll workers have the same efficiency.
ExplanationMan-days = 72; 8 workers ⇒ 9 days. Statement II alone lacks worker count. Answer: A.