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Q:

P can complete a work in 12 days working 8 hours a day.Q can complete the same work in 8 days working 10 hours a day. If both p and Q work together,working 8 hours a day,in how many days can they complete the work?

A) 60/11 B) 61/11
C) 71/11 D) 72/11

Answer:   A) 60/11



Explanation:

P can complete the work in (12 * 8) hrs = 96 hrs

Q can complete the work in (8 * 10) hrs=80 hrs

\inline {\color{Black}\therefore } P's 1 hour work=1/96   and Q's 1 hour work= 1/80

(P+Q)'s 1 hour's work =\inline {\color{Black} \left ( \frac{1}{96}+\frac{1}{80} \right )} =\inline {\color{Black} \frac{11}{480}}

so both P and Q will finish the work in \inline {\color{Black} \frac{480}{11}} hrs

\inline {\color{Black} \therefore } Number of days of 8 hours each = \inline {\color{Black} \left ( \frac{480}{11} \times \frac{1}{8}\right )=\frac{60}{11}}

Q:

A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left?

A) 8/15 B) 7/9
C) 6/13 D) 4/11
 
Answer & Explanation Answer: A) 8/15

Explanation:
P's 1 day's work = 1  
15
Q's 1 day's work = 1  
20
(P + Q)'s 1 day's work = ( 1 + 1 ) = 7  
15 20 60
(P + Q)'s 4 day's work = ( 7 x 4 ) = 7  
60 15
Therefore, Remaining work = ( 1 - 7 ) = 8 .
15 15
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1 32
Q:

X can complete the work in 10 days, Y can do the same in 15 days. If they are hired for 5 days to do the work together, what is the work that left unfinished?

A) 1/3 B) 2/3
C) 1/6 D) 5/6
 
Answer & Explanation Answer: C) 1/6

Explanation:

Given X can do in 10 days

=> 1 day work of X = 1/10

Y can do in 15 days

=> 1 day work of Y = 1/15

1day work of (X + Y) = 1/10 + 1/15 = 1/6

Given they are hired for 5 days

=> 5 days work of (X + Y) = 5 x 1/6 = 5/6

Therefore, Unfinished work = 1 - 5/6 = 1/6 

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8 251
Q:

If 10 men take 15 days to complete a work. In how many days will 37 men complete the work?

A) 3 days B) 4 days
C) 5 days D) 6 days
 
Answer & Explanation Answer: B) 4 days

Explanation:

Given 10 men take 15 days to complete a work

=> Total mandays = 15 x 10 = 150

Let the work be 150 mandays.

=> Now 37 men can do 150 mandays in 150/37 =~ 4 days

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12 189
Q:

Three taps P, Q and R can fill a tank in 12 hrs, 15 hrs and 20 hrs respectively. If P is open all the time and Q and R are open for one hour each alternately, starting with Q, then the tank will be full in how many hours ?

A) 9 hrs B) 7 hrs
C) 13 hrs D) 11 hrs
 
Answer & Explanation Answer: B) 7 hrs

Explanation:

Given,

P can fill in 12 hrs

Q can fill in 15 hrs

R can fill in 20 hrs

=> Volume of tank = LCM of 12, 15, 20 = 60 lit

=> P alone can fill the tank in 60/12 = 5 hrs

=> Q alone can fill the tank in 60/15 = 4 hrs

=> R alone can fill the tank in 60/20 = 3 hrs

Tank can be filled in the way that

(P+Q) + (P+R) + (P+Q) + (P+R) + ....

=> Tank filled in 2 hrs = (5+4) + (5+3) = 9 + 8 = 17 lit

=> In 6 hrs = 17 x 6/2 = 51 lit

=> In 7th hr = 51 + (5+4) = 51 + 9 = 60 lit

=> So, total tank will be filled in 7 hrs.

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7 366
Q:

P and Q can complete a job in 24 days working together. P alone can complete it in 32 days. Both of them worked together for 8 days and then P left. The number of days Q will take to complete the remaining work is ?

A) 56 days B) 54 days
C) 60 days D) 64 days
 
Answer & Explanation Answer: D) 64 days

Explanation:

(P+Q)'s 1 day work = 1/24

P's 1 day work = 1/32

=> Q's 1 day work = 1/24 - 1/32 = 1/96

Work done by (P+Q) in 8 days = 8/24 = 1/3

Remainining work = 1 - 1/3 = 2/3

Time taken by Q to complete the remaining work = 2/3 x 96 = 64 days.

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6 370