Puzzles contest - 11 With Answers

[HELP]

1. Two identical trains, at the equator start travelling round the world in opposite directions. They start together. run at the same speed and are on different tracks.Which train will wear out its wheel treads first?

2. Next door to me live four brothers of different heights. Their average height is 74 inches, and the difference in height amongst the first three men is two inches. The difference between the third and the fourth man is six inches. Can you tell how tall is each brother?

3. Fifty minutes ago if it was four times as many minutes past three o'clock. how many minutes is it to six o'clock?

4. while in San Francisco some time back, I hired a car to drive over the Golden Gate bridge. I started in the afternoon when there was no traffic rush. So J could drive at a speed of 40 miles an hour. While 0 returning. however. I got caught in the traffic rush and I could only manage to drive at a speed of 25 miles an hour. What was my average speed for the round trIp?




5. A family I know has several children. Each boy in this family has as many sisters as brothers but each girl has tWice as many brothers as sisters. How many brothers and sisters are there?






Answers :



1. Naturally, the train travelling against the spin of the earth. This train will wear out its wheels more quickly, because the centrifugal force is Less on this train



2. The first brother is 70 inches tall, th~ second 72, the third 74 and the fourth brother 80 inches tall.

3. Twenty-six minutes.

4. No, the answer is not 321/2 miles an hour, though this figure is the obvious answer! However. this represents the average of the 2 speeds and not the average speed for the whole trip.If the time is equal to the distance divided by theaverage speed, then the time for the trip starting from San Francisco equals 5/40 and the time for the return




5. Since the boys have as many brothers as sisters, there must be 1 boy more than the number of girls. If we try 2 and 1,3 and 2, and 4 and 3, we will find that 4 boys aild 3 girls is the solution to fulfil the requirement that each girl has twice as many brothers as sisters







Edited by: HELP

[prethi]

lets assumeA B C D r persons n x be height of A


thn thr heightswill be


a=x


b=?


c=x-2


d=x-8


a+b+c+d=296


v need some other inf to be specified to get unique value of x


am i correct???????????????


prethi

[JotiN]

1.

5. 4 brothers and 3 sisters

[sakshi_arora4]

ans 1)


trin running against the spin of the earth will wear out the wheel threads first.


ans 2)let height of first brother is x.


ht of second would be x-2.


third would be x-4


fourth would be x-10.


so x+(x-2)+(x-4)+(x-10)=74


ans 3)26 min to 6 o'clock


let present time be x


x-50=4y


x+y=180


where y is the time past 3.


let 3:00 is taken as 0 minutes.thus 6:00 would be 180 min.


y=26 minutes.


ans 4)400/13


avg speed is (2*s1*s2)/(s1+s2)


where s1 n s2 r 2 speeds given.


(2*40*25)/(40+25)


ans 5)family has 4boys n 3 girls.

[keerthi]

2. Next door to me live four brothers of different heights. Their average height is 74 inches, and the difference in height amongst the first three men is two inches. The difference between the third and the fourth man is six inches. Can you tell how tall is each brother?
Ans)70 ,72,74,80

Let theheights of first three be x-2 , x , x+2
theheight of fourth = x+8
(x-2+x+x+2+x+8)/4 = 74
(4x+8)/4 = 74
x+2 = 74
x = 72

so their heights are 70 ,72 , 74 , 80Edited by: keerthi

[keerthi]

3. Fifty minutes ago if it was four times as many minutes past three o'clock. how many minutes is it to six o'clock?
Ans) 26 min



let it b "X" min to six o' clk.
as per ques we get time past 3 o'clk as 4X.



current time=4X+50 minutes from 3 o' clk.
no. of minutes between 3 and 6pm =180.
hence current time by counting back from 6 o'clk =180-X


so 4X+50=180-X.
hence we get X=26min.

[keerthi]

4. while in San Francisco some time back, I hired a car to drive over the Golden Gate bridge. I started in the afternoon when there was no traffic rush. So J could drive at a speed of 40 miles an hour. While 0 returning. however. I got caught in the traffic rush and I could only manage to drive at a speed of 25 miles an hour. What was my average speed for the round trIp?

Ans) 30.76mph

Let the distance be 'x'
time for forward journy = x/40
time for return journey = x/25
total time = x/40+x/25 = 13 x/200
average speed = total diatance / total time = 2x /(13x/200) = 400/13 =30.76 mph
Edited by: keerthi

[keerthi]

5. A family I know has several children. Each boy in this family has as many sisters as brothers but each girl has tWice as many brothers as sisters. How many brothers and sisters are there?

Ans) 4 brothers and 3 sisters

[rajesh kumar]

5.A family I know has several children. Each boy in this family has as many sisters as brothers but each girl has tWice as many brothers as sisters. How many brothers and sisters are there?


answer:


Each boy in this family has as many sisters as brothers :


X+1 boys = X girls


each girl has tWice as many brothers as sisters:


X+1 boys = 2*(X-1) girls


by solving above eqn


X=3.


hence,


Ans:4 boys(X+1) & 3 girls(X)

[Dr YVS]

QN 2 can have another answer..


a, a-2, a-4, a-10 Sum = 4a-16=4*74=296 Hence the heights are


78,76,74,68 ( sum = 296)

[pavankumarj]

2. Next door to me live four brothers of different heights. Their average height is 74 inches, and the difference in height amongst the first three men is two inches. The difference between the third and the fourth man is six inches. Can you tell how tall is each brother?[/b]
Ans)70 ,72,74,80

Let theheights of first three be x-2 , x , x+2
theheight of fourth = x+8
(x-2+x+x+2+x+8)/4 = 74
(4x+8)/4 = 74
x+2 = 74
x = 72

so their heights are 70 ,72 , 74 , 80