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.
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 Easy
A completes a job in 10 days. In 5 days he completes:
ExplanationRate = 1/10 per day; in 5 days = 5/10 = 1/2. -
Q2 Easy
B finishes work in 15 days. Daily part of job is:
ExplanationRate = 1/15 per day. -
Q3 Medium
A (10 days) and B (15 days) together finish in:
ExplanationCombined rate = 1/10 + 1/15 = 1/6; time = 6 days. -
Q4 Hard
For “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. -
Q5 Medium
12 men finish a job in 8 days. 16 men finish in:
ExplanationMan-days = 96; 96/16 = 6 days. -
Q6 Hard
Pipe 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. -
Q7 Easy
A does twice the work of B in the same time. Ratio of efficiencies A : B is:
ExplanationTwice the work ⇒ twice the rate.
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Q8 Medium
For “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. -
Q9 Medium
A works 4 days and completes 2/5 of a job. Whole job takes A:
Explanation4 days = 2/5 ⇒ full job = 10 days. -
Q10 Medium
Three equal workers finish in 9 days. One worker finishes in:
ExplanationTotal man-days = 27; one worker = 27 days. -
Q11 Hard
A is 50% more efficient than B. If B takes 18 days, A takes:
ExplanationA rate = 1.5 × B rate; time ratio 2 : 3; A = 12 days. -
Q12 Easy
For “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. -
Q13 Easy
Work done in 3 days at 1/8 job per day is:
Explanation3 × 1/8 = 3/8. -
Q14 Hard
6 machines of same capacity make 240 units in 5 days. 4 machines make 240 units in:
ExplanationMachine-days = 30; 4 machines need 30/4 = 7.5 days.
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DS1 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. -
DS2 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.
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DS3 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. -
DS4 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.