@viewpt said:Q: How many nos. (n) are there b/w 1 and 200 such that n/2, n/3 and (2n+1)/5 are all composite natural nos.?
Is the ans 1?? No = 162
No = 192 @ScareCrow28 said:Ek aur no aya No = 192
@ScareCrow28 said:Ans kya h?? 2?
ANS IS CORRECT .. APPROACH?
@viewpt said:approach bayan karo::
No is of the form 6k
Also 2(6k) + 1 = 5*l
Hence 12k+1 = 5*l
=> k = 5a + 2
Now, n = 6k = (30a + 12)
Now, 1
=> 30a + 12
=> a
=> a = 0, 1, 2, 3, 4, 5, 6
Nos are = 12, 42, 72, 102, 132, 162 and 192
We can easily see that only 162 and 192 satisfy
@ScareCrow28 said:No is of the form 6k Also 2(6k) + 1 = 5*lHence 12k+1 = 5*l=> k = 5a + 2Now, n = 6k = (30a + 12)Now, 1=> 30a + 12 => a => a = 0, 1, 2, 3, 4, 5, 6Nos are = 12, 42, 72, 102, 132, 162 and 192We can easily see that only 162 and 192 satisfy
bhai mujhe confusion ho rahi hai.. how 162 and 192 are satisfying..ye 'a' kahan se introduce kar diya??
@viewpt said:bhai mujhe confusion ho rahi hai.. how 162 and 192 are satisfying..
162/2 = 81 = Composite
162/3 = 54 = Composite
(2*162 + 1)/5 = 325/5 = 65 = Composite
Similarly for 192
"a" is nothing but some no and k should be of the form = 5a + 2
Only then will the no (2n+1) be divisible by 5..
@shinoda said:1) the area of the circle circumscribing three circles of unit radius touchnig each other is ?
Symmetry lagao.. ( aur thodi trigo ) Connect the centres of inner circles you will find that it makes an equilateral traingle!
So Radius of bigger circle will come out to be (1+2/root(3))
hence Area = pie/3 * (2 + root(3) )^2
In the suniti building in mumbai there are 12 floors plus the ground floor.9 people get into the lift of the building on the ground floor.the lift does not stop on the first floor.If 2,3 and 4 alight from lift on the upward journey,how many ways can they do so?(a)11c3*3p3 (b)11p3*9c4*5c3 (c) 10p3*9c4*5c3 (d) 12 c3
@ani6 said:In the suniti building in mumbai there are 12 floors plus the ground floor.9 people get into the lift of the building on the ground floor.the lift does not stop on the first floor.If 2,3 and 4 alight from lift on the upward journey,how many ways can they do so?(a)11c3*3p3 (b)11p3*9c4*5c3 (c) 10p3*9c4*5c3 (d) 12 c3
b??
@ani6 said:In the suniti building in mumbai there are 12 floors plus the ground floor.9 people get into the lift of the building on the ground floor.the lift does not stop on the first floor.If 2,3 and 4 alight from lift on the upward journey,how many ways can they do so?(a)11c3*3p3 (b)11p3*9c4*5c3 (c) 10p3*9c4*5c3 (d) 12 c3
b ?
9C4*(11) * 5C3*(10) * 9 = 11p3*9c4*5c3 ..
@shinoda said:1) the area of the circle circumscribing three circles of unit radius touchnig each other is ?
ans1: pi* [(2 + rt(3)]^2/3
@shinoda said:2)find the ratio of diamter of the circles inscribed in and circumscribing an equilateral triangle to its height. ?
ans 2: 2:4:3
@ani6 said:In the suniti building in mumbai there are 12 floors plus the ground floor.9 people get into the lift of the building on the ground floor.the lift does not stop on the first floor.If 2,3 and 4 alight from lift on the upward journey,how many ways can they do so?(a)11c3*3p3 (b)11p3*9c4*5c3 (c) 10p3*9c4*5c3 (d) 12 c3
OA) b
@ani6 said:@ScareCrow28 yes plz explain in detail
Question says the people alight in groups of 2, 3 and 4
Take any 4 in 9C4 ways. Now these 4 people have 11 options ( Floor#2 - Floor#12)
Left is group of 3 people, take 'em in 5C3 ways..they have 10 options ( Because 1 of the floors has been used up by the group of 4 )
Left = 2 people = 2C2 ways..Floor options = 9
Total = 9C4(11)*5C3(10)*2C2(9) = 11P3*9C4*5C3..
There are three pipes, A, B and C, opening into a tank. Each pipe can be used to fill or empty the tank at the same respective rate. The ratio of the rates of the three pipes at which they either fill or empty the tank is 2 : 3 : 4. Pipes A and B, working together, take 3 hours to fill the tank when both are used as inlet pipes. In the first, second and third hours of operation, the pipes, A, B and C respectively are used as emptying pipes, while the other two pipes are used as filling pipes. What is the fraction of the tank to be filled at the end of the three hours ?
There are three pipes, A, B and C, opening into a tank. Each pipe can be used to fill or empty the tank at the same respective rate. The ratio of the rates of the three pipes at which they either fill or empty the tank is 2 : 3 : 4. Pipes A and B, working together, take 3 hours to fill the tank when both are used as inlet pipes. In the first, second and third hours of operation, the pipes, A, B and C respectively are used as emptying pipes, while the other two pipes are used as filling pipes. What is the fraction of the tank to be filled at the end of the three hours ?
@ani6 said:@ScareCrow28 yes plz explain in detail
No. of ways of getting down= 11P3
choosing 4 people = 9C4
choosing 3 people= 5C3
total= 11P3*9C4*5C3