Time speed, work, Alligations and mixtures problems

[mattoo]

A Shatabadi Express train, owing to a defect in the engine, goes at 5/8 of its proper speed and arrives at 6.49 pm instead of 5.55pm. at what hour did it start?
a)4.15 pm
b)4.35 pm
c)4.25 pm

[srikar2097]

Originally Posted by mattoo

A Shatabadi Express train, owing to a defect in the engine, goes at 5/8 of its proper speed and arrives at 6.49 pm instead of 5.55pm. at what hour did it start?
a)4.15 pm
b)4.35 pm
c)4.25 pm

d=s*t
d=5s/8 * (t+54/60)
solve, we get t=1.5hrs.
Start time = 5:55pm - 1.5hrs = 4:25pm

Hence (c)

[racer_jo]

Hi,
Can anyone explain how to approach the problems in concerning time gained/lost by a faulty clock? Here's one of them:
The hour and the minute hands of faulty clock coincide every 64 minutes. How much time will the clock gain/loose in a day?

Regards,

[sayuz_enigma]

Originally Posted by mattoo

A Shatabadi Express train, owing to a defect in the engine, goes at 5/8 of its proper speed and arrives at 6.49 pm instead of 5.55pm. at what hour did it start?
a)4.15 pm
b)4.35 pm
c)4.25 pm

Because of the reduced speed, the distance which the train normally covers in 1 hr, would be covered in 8/5hrs = 1hr 36 mins.
Thus for a normal 1 hr journey, it runs 36 mins late
In this particular journey,It is running 6:49-5:55 = 54 mins late...
Therefore, original duration of journey was 54/36 = 1hr 30 mins
Therefore the train started at 5:55-1:30 = 4:25pm, hence (c)

[Amz0625]

16 men and 12 Boys can complete a work in 26 days . 13 men can complete the same work in 48 days .In how many days will 12 men and 6 boys complete half work ?
a 8
b 12
c 4
d none of these


Question2

18 Men and 12 Girls can do a work in 18 days . A girl takes twice as much time as a man to do the work . How many days will 8 men take to finish the same work ?
a 45
b 50
c 54
d None of these

Question 3
A man , a woman and a boy can finisha work in 20,30,60 days respectively. How many boys must assist 2 men and 8 women to do the work in 2 days ?
a 4 boys
b 5 boys
c 6 boys
d None
Question 4

A garison has food sufficent for a certain number of days for certain men. After 40 days 1/4th of the men left and it is found that the food will now last as long as before , how long was that ?
a 100days
b 120
c 160
d 180

[srikar2097]

16 men and 12 Boys can complete a work in 26 days . 13 men can complete the same work in 48 days .In how many days will 12 men and 6 boys complete half work ?
a 8
b 12
c 4
d none of these

Is the answer (D) None?

My approach-
13M->26 days
=> 12B = 8M or 6B=4M
=> 12M+6B=16M
=> 39 days for full work. But only half work needs to be done, i.e. 39/2 =19.5 days.

[srikar2097]

Question2
18 Men and 12 Girls can do a work in 18 days . A girl takes twice as much time as a man to do the work . How many days will 8 men take to finish the same work ?
a 45
b 50
c 54
d None of these

Answer (C)

Given, 1M=2G
=>18M+12G = 24M take 18 days
so 8 men take 54 days.

[srikar2097]

Question 3
A man , a woman and a boy can finisha work in 20,30,60 days respectively. How many boys must assist 2 men and 8 women to do the work in 2 days ?
a 4 boys
b 5 boys
c 6 boys
d None

Answer (D)

Given, 2M=3W=6B
=> 2M+8W=22B
Let x more boys be needed.
=>if 1B takes 60 days, then for (22+x) boys to do the same in 2 days, we need x=8B

[Amz0625]

Answers are

1, D
2. C
3. D
4. C iam not sure of this one ill confirm after sometime

[minisingh]

Originally Posted by srikar2097

My approach-
13M->26 days
=> 12B = 8M or 6B=4M
=> 12M+6B=16M
=> 39 days for full work. But only half work needs to be done, i.e. 39/2 =19.5 days.

I got 19 days by conventional method (equating 1 day work) for both man and boy, But i didnt understand how did u equate 12B=8M and then went around.

Kindly elaborate