@kingsleyx said:Carl walks over a railway-bridge. At the moment that he is just ten meters away from the middle of the bridge, he hears a train coming from behind. At that moment, the train, which travels at a speed of 90 km/h, is exactly as far away from the bridge as the bridge measures in length. Without hesitation, Carl rushes straight towards the train to get off the bridge. In this way, he misses the train by just four meters! If Carl would, however, have rushed exactly as fast in the other direction, the train would have hit him eight meters before the end of the bridge.What is the length of the railway-bridge?
44?
@kingsleyx said:In a class are twenty-six children. None of the children was born on February 29th. What is the probability that at least two children have their birthdays on the same day?
1-(365P26/365^26)?
@kingsleyx said:In a class are twenty-six children. None of the children was born on February 29th. What is the probability that at least two children have their birthdays on the same day?
Means tat the 26 children can be born on 366-1=365 days
Atleast 2 children on sameday = 1- all different
P(all diff)= (365/365)*(364/365)*......340/365
Hence ans wil be 1-((365/365)*(364/365)*......340/365 )
15.The seven-digit number 1468 x 8y is divisible by 4. Find the probability that it is also divisible by 9.
1/15
2/15
1/5
4/15
1/15
2/15
1/5
4/15
i am getting the cases like for y = 0, x= 0 or 9
for y = 4, x = 5
for y = 8, x=1 but unable to proceed further.
@rachit_28 said:15.The seven-digit number 1468 x 8y is divisible by 4. Find the probability that it is also divisible by 9.1/152/151/54/15i am getting the cases like for y = 0, x= 0 or 9for y = 4, x = 5for y = 8, x=1 but unable to proceed further.
2/15?
@rachit_28 said:15.The seven-digit number 1468 x 8y is divisible by 4. Find the probability that it is also divisible by 9.1/152/151/54/15i am getting the cases like for y = 0, x= 0 or 9for y = 4, x = 5for y = 8, x=1 but unable to proceed further.
2/15??
@rachit_28 said:15.The seven-digit number 1468 x 8y is divisible by 4. Find the probability that it is also divisible by 9.1/152/151/54/15i am getting the cases like for y = 0, x= 0 or 9for y = 4, x = 5for y = 8, x=1 but unable to proceed further.
Must be 2/15
y=0,4,8 => for each value 10 cases of x are possible such that the no is divisble by 4
So 10*3=30 nos divisible by 4
Of these
when y=0,x=0,x=9 2 possible values
y=4,x=1 possible value
y=8,one possible value So total 2+1+1=4
Hence out of 30 nos ,4 are divisble both by 4 and 9
4/30=2/15
@rachit_28 said:bhaiyo kaise ?
U have got 4 cases where its divisible by 9 right. now count the total cases where it can be divisible by 4 . i.e when y =0, x=0-9; when y=4,x=0-9,; and when y=8, x=0-9. therfore a total of 30. hence the probability is 4/30=2/15
@rachit_28 said:bhaiyo kaise ?
total cases(y=0,4,8 and x=0 to 9)=3x10=30
now sum of digits = 27+ x +y......for it 2 be divisible by 9
case1........x+y=0=>x=0,y=0
case2.......x+y=9=>x=9,y=0
x=5,y=4
x=1,y=8
favourable cases=4
req prob=4/30=2/15
now sum of digits = 27+ x +y......for it 2 be divisible by 9
case1........x+y=0=>x=0,y=0
case2.......x+y=9=>x=9,y=0
x=5,y=4
x=1,y=8
favourable cases=4
req prob=4/30=2/15
At a certain stationery store, only 4 varities of pen and 4 varities of pencils are sold. the price of one of each of the 4 varities of pen is Rs 45. The price of a set of each of the four varities of pencil is Rs 12. The price of the cheapest pencil is Rs 1 and the combined price of 3 of the varities of pens are exactly twice the combined price of the other 3 varities of pencils. What is price of the costliest variety of pen?
@gupanki2 said:At a certain stationery store, only 4 varities of pen and 4 varities of pencils are sold. the price of one of each of the 4 varities of pen is Rs 45. The price of a set of each of the four varities of pencil is Rs 12. The price of the cheapest pencil is Rs 1 and the combined price of 3 of the varities of pens are exactly twice the combined price of the other 3 varities of pencils. What is price of the costliest variety of pen?
23??
@gupanki2 said:@kingsleyx Yes... correct.. approach pls??? :S
Cost of the 4 pencils together =12. The cheapest is 1. The cost of the other three varieties of pencils is 12-1=11.
We know that the combined price of 3 of the varieties of pens are exactly twice the combined price of the other 3 varieties of pencils --> 2*11 = 22.
as the total cost of the all the 4 pens is 45 and three pens cost 22. one shud cost 45-22=23 and it wud be the costliest !!
@kingsleyx said:Carl walks over a railway-bridge. At the moment that he is just ten meters away from the middle of the bridge, he hears a train coming from behind. At that moment, the train, which travels at a speed of 90 km/h, is exactly as far away from the bridge as the bridge measures in length. Without hesitation, Carl rushes straight towards the train to get off the bridge. In this way, he misses the train by just four meters! If Carl would, however, have rushed exactly as fast in the other direction, the train would have hit him eight meters before the end of the bridge.What is the length of the railway-bridge?
(speed of carl = S, length of bridge = 2L)
when Carl runs towards the train
=> (2L-4)/90 = (L-10)/S....................(i)
When Carl runs away from the train
=> (2L-8+4)/90 = {(2L-8)-(2L-20)}/S
=>(2L-4)/90 = 12/S.............(ii)
dividing (i) and (ii) we get
12=(L-10)
=>2L = 44m.
ATDH.