A man can do a work in 20 days and a woman in 15 days. If they work on it together for 5 days, then the fraction of the work that is left-
A
8/15
B
1/12
C
5/12
D
None of these
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Question: A man can do a work in 20 days and a woman in 15 days. If they work on it together for 5 days, then the fraction of the work that is left-
Solution:
Man's 1 day's work = 1/20
Woman's 1 day's work = 1/15
∴ (Man + woman)'s 1 day's work = (1/20) + (1/15) = (3 + 4)/60 = 7/60
∴ (Man + woman)'s 5 day's work = (7/60) × 5 = 7/12
Thus, Remaining work = 1 - (7/12) = (12 - 7)/12 = 5/12
∴ The fraction of the work that is left = 5/12
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Updated: 2 weeks ago
A can complete a piece of work in 36 days, B in 54 days and C in 72 days. All the three began the work together but A left 8 days before the completion of the work and B 12 days before the completion of work. Only C worked up to the end. In how many days was the work completed?
Created: 2 weeks ago
A
18 days
B
24 days
C
28 days
D
36 days
Question: A can complete a piece of work in 36 days, B in 54 days and C in 72 days. All the three began the work together but A left 8 days before the completion of the work and B 12 days before the completion of work. Only C worked up to the end. In how many days was the work completed?
Solution:
Let the work be completed in y days. C works for y days
Therefore, A works for (y - 8) days
B works for (y - 12) days.
According to the question,
{(y-8)/36} + {(y - 12)/54} + (y/72) = 1
⇒ 6(y - 8) + 4 (y - 12) + 3y = 216
⇒ 6y - 48 + 4y - 48 + 3y = 216
⇒ 13y = 216 + 96 = 312
⇒ y = 312/13
∴ y = 24
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Updated: 2 weeks ago
If 5 workers can paint a house in 8 hours, how long would it take 20 workers to paint the same house?
Created: 1 week ago
A
2 hours
B
3 hours
C
5 hours
D
1 hours
Question: If 5 workers can paint a house in 8 hours, how long would it take 20 workers to paint the same house?
Solution:
5 workers can paint a house in 8 hours
∴ 1 worker would take = (8 × 5) hours
∴ 20 workers would take = (8 × 5)/20 hours
= 2 hours
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Updated: 1 week ago
A takes three times as much time as B or twice as much time as C to finish a piece of work. Working together, they can finish the work in 3 days. B can do the work alone in how many days?
Created: 1 week ago
A
14 days
B
8 days
C
6 days
D
10 days
Question: A takes three times as much time as B or twice as much time as C to finish a piece of work. Working together, they can finish the work in 3 days. B can do the work alone in how many days?
Solution:
ধরা যাক,
A, B ও C যথাক্রমে কাজটি শেষ করতে সময় লাগে x, x/3, এবং x/2 দিন।
তারা একসাথে ৩ দিনে কাজ শেষ করে।
অর্থাৎ তাদের একদিনের কাজ হলো 1/3।
∴ A + B + C এর একদিনের কাজ = (1/x) + (3/x) + (2/x)
= (1 + 3 + 2)/x
= 6/x
এখন,
6/x = 1/3
∴ x = 18
∴ B একা কাজ শেষ করতে সময় নেবে = 18/3 = 6 দিন।
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Updated: 1 week ago
