Govt. Exams
Entrance Exams
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Topics in Quantitative Aptitude
A contractor agrees to build a bridge in 300 days. He employs 10 workers. After 150 days, he finds that only half the work is complete. How many additional workers does he need to finish on time?
Correct Answer:
B. 10 workers
EXPLANATION
Remaining days = 150. Remaining work = 1/2. Current productivity = (1/2 work)/(150 days × 10 workers) = 1/3000 per worker-day. Required rate = (1/2)/(150 × x) where x is total workers. x = 10. So need 10 additional workers.
A, B, and C can complete a work in 6 days, 8 days, and 12 days respectively. A and B work for 2 days, then C joins them. How many more days will they take to complete the remaining work?
Correct Answer:
B. 2 days
EXPLANATION
A+B rate = 1/6 + 1/8 = 7/24.
Work in 2 days = 14/24 = 7/12.
Remaining = 5/12.
All three rate = 1/6 + 1/8 + 1/12 = 9/24 = 3/8.
Days = (5/12)/(3/8) = 40/36 ≈ 1.11, recalculating: remaining work done in 2 days
If A works for 3 days and B works for 2 days, they complete 1/4 of work. If A works for 2 days and B works for 3 days, they complete 1/3 of work. How many days does A take to complete the work alone?
Correct Answer:
A. 30 days
EXPLANATION
Let A's rate = 1/x, B's rate = 1/y.
From equations: 3/x + 2/y = 1/4 and 2/x + 3/y = 1/3.
Solving: x = 30 days
