sanjali wrote:

Please give the solution

1) A is thrice as good a workman as B and takes 10 days less to do a piece of work than B takes. the number of days taken by B to finish the work is:

a) 12

b) 15

c) 20

d) 30

R*3 *(D-10) = R * D

3RD - 30R = RD

2RD = 30R

D = 15.

R is the rate and D is the days. B

2) A does half as much work as B in 3/4 of the time. If together they take 18 days to complete the work, how many days will B take to do it?

a) 30

b) 35

c) 40

d) 45

D?

A = 3/2*R since it says it takes to do HALF unit of work in 3/4 rate of B. since we need to keep the rate to 1unit of work we multiply by 2 to get 3/2R for A. Now we find R by doing: (3/2R +R) *18 = 1 since they combined to get 1 work done in 18 days. we find R ~= .0222 and plug into R*D = 1 we get ~=45

3) A works twice as fast as B. If B can complete a piece of work independently in 12 days, then the number of days taken by A and B together to finish the work is:

a) 4

b) 6

c) 8

d) 18

A. I first looked at it and used POE to find the answer. If B takes 12 days, A takes 6 days so we KNOW combining it has to be lower than 6 so A.

Here is analytical:

A=.1/6 B = 1/12 (1/6+1/12)D=1 D=4

remember the rate of work is 1 work/time. since they gave that it takes 12 days to do 1 work it is just 1/12 rate.

4) A and B working separately can do a piece of work in 9 and 12 days respectively.If they work for a day alternately, A beginning, in how many days, the work will be completed?

a) 10 1/2

b) 10 1/4

c) 10 2/3

d) 10 1/3

B

A = 1/9 B=1/12

i gonna "cheat" here and go straight to final day (since answer choice give us that advantage). so we know each worked 5 days so total work done so far is:

5/9+5/12 =.97222 We know last day is A's turn so we have 1/9 * D = (1-.97222) D = .25 so B

5) 8 men can dig a pit in 20 days. if a man works half as much again as a boy, then 4 men and 9 boys can dig it in:

a) 10 days

b) 12 days

c) 15 days

d) 16 days

C?

8*R *20 = 1 R=.00625 for ONE Man

(2*R+9*R)D = 1 11R*D =1 D = 14.5 = 15.

6) A cistern has a leak which would empty it in 8 hours. A tap is turned on which admits 6 liters a minute into the cistern and it is now empited in 12 hours. how many litres does the cistern hold.

a) 7580

b) 7960

c) 8290

d) 8640

D.???

C = X/8H T = 6L/M = 360L/H

Since tap is turned on for 12 hours we have 360*12 = 4320L for 12 hours

X/8 *12 = 4320+X .5X = 4320 X=8640???? The rate is still X liters / 8 hours but multiplied by 12 now. It is STILL ONE UNIT OF WORK on the right BUT we know how much that work is - 4320 (max water from tap) + X(unknown amount in cistern).

7) two pipes M and N can fill a cistern in 24 min and 32 min , repectively. If both the pipes are opened together, then after hoe many minutes N should be closed so that the tank is full in 18 minutes ?

a) 6

b) 8

c) 10

d) 21

B.

M = 1/24 N = 1/32

1/24*18 + 1/32*(18-M)=1

18-M = 8 M=10 so 18-10 =8 B

If anyone has a faster way to do any of these or shortcuts please share. I also understand some of the calculations i did it right off a calculator and you should know how to do it with fractions!!!

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