20
Q:

A can do a certain work in the same time in which B and C together can do it.If A and B together could do it in 20 days and C alone in 60 days ,then B alone could do it in:

A) 20days B) 40 days
C) 50 days D) 60 days

Answer:   D) 60 days



Explanation:

(A+B)'s 1 day's work=1/20

C's 1 day work=1/60

(A+B+C)'s 1 day's work=\inline {\color{Black} \left ( \frac{1}{20} + \frac{1}{60}\right )=\frac{4}{60}=\frac{1}{15}}

Also A's 1 day's work =(B+C)'s 1 day's work

\inline {\color{Black} \therefore } we get: 2 * (A's 1 day 's work)=1/15

=>A's 1 day's work=1/30

\inline {\color{Black} \therefore } B's 1 day's work= \inline {\color{Black} \left ( \frac{1}{20} -\frac{1}{30}\right )=\frac{1}{60}}

So, B alone could do the work in 60 days.

Q:

A town having teenagers(boys & girls) of 5000 requires 150 litre of water per head. It has a tank measuring 20 m × 15 m × 5 m. The water of this tank will sufficient for ____ days.

A) 8 B) 6
C) 4 D) 2
 
Answer & Explanation Answer: D) 2

Explanation:

Total Water reqduired = 5000 × 150 lit

= 750,000 litres = 750 cu.m.

Volume of tank = 20 × 15 × 5 = 1500 Cu.m.

Number of days required =1500/750 = 2 days.

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0 9
Q:

Priya can do a work in 16 days. In how many days will the work be completed by Sai, if the efficiency of Sai is 60% more than that of Priya ?

A) 8 days B) 12 days
C) 14 days D) 10 days
 
Answer & Explanation Answer: D) 10 days

Explanation:

Ratio of efficiencies of Priya and Sai is

Sai : Priya = 160 : 100 = 8 : 5

Given Priya completes the work in 16 days

Let number of days Sai completes the work be 'd'

=> 5×16 = 8×d

d = 10 days.

Therefore, number of days Sai completes the work is 10 days.

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7 181
Q:

Pavan and Sravan are two persons. If Pavan works with his actual efficiency and Sravan twice of his actual efficiency then it takes 25 days to complete the work. But If Pavan works twice of his actual efficiency and Sravan with his normal efficiency then the work is completed in 20 days. How many days would it take if Sravan alone works with his actual efficiency (in Days)?

A) 50 B) 100
C) 70 D) 35
 
Answer & Explanation Answer: B) 100

Explanation:

Let the Efficiency of pavan be E(P)

Let the Efficiency of sravan be E(S)

Here Work W = LCM(25,20) = 100

Now, E(P+2S) = 100/25 = 4 ....(1)

E(2P+S) = 100/20 = 5 ....(2)

Hence, from (1) & (2) we get

E(S) = 1

=> Number of days Savan alone work to complete the work  = 100/1 = 100 days.

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9 155
Q:

A contractor undertake to finish a certain work in 124 days and employed 120 men. After 64 days, he found that he had already done 2/3 of the work. How many men can be discharged so that the work may finish in time ? 

A) 64 B) 62
C) 58 D) 56
 
Answer & Explanation Answer: D) 56

Explanation:

Days remaining 124 – 64 = 60 days

Remaining work = 1 - 2/3 = 1/3

Let men required men for working remaining days be 'm'

So men required = (120 x 64)/2 = (m x 60)/1 => m = 64

Men discharge = 120 – 64 = 56 men.

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6 362
Q:

A can build a wall in 16 days while B can destroy it in 8 days. A worked for 5 days. Then B joined with A for the next 2 days. Find in how many days could A build the remaining wall ?

A) 12 days B) 14 days
C) 13 days D) 16 days
 
Answer & Explanation Answer: C) 13 days

Explanation:

Now, Total work = LCM(16, 8) = 48

A's one day work = + 48/16 = + 3

B's one day work = - 48/8 = -6

Given A worked for 5 days to build the wall => 5 days work = 5 x 3 = + 15

2days B joined with A in working = 2(3 - 6) = - 6

Remaining Work of building wall = 48 - (15 - 6) = 39

Now this remaining work will be done by A in = 39/3 = 13 days.

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8 284