Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill it in 7 hours. The number of hours taken by C alone to fill the cistern, is:
Part filled in 2 hours = 2/6 = 1/3. Remaining part = 2/3
(A + B)'s 7 hours' work = 2/3.
So, (A+B)'s 1 hr work = 2/21
Therefore C's 1 hour's work
= [(A+B+C)'s 1 hour]-[(A+B)'s 1 hr work]
=(1/6 - 2/21) = 1/14
C alone can fill the tank in 14 hours
There are two bags. First contain 10 white and other 8 red balls. One ball from any bag is shifted to other bag at random. What will be the probability that second ball taken after first event would be red. First event is to drawn first ball.
Initial condition 10W 8R
After first event two possibilities arise
9W
8R;1W
10W, 1R
7R
Choice of any has probability 1/2 so overall probability for getting red ball
= 1/2(1/2*0 + 1/2*8/9) + 1/2(1/2*1/11 + 1/2*1)
solve
49/99
Option 8)
If x^2 - y^3 is a positive non zero integer for all possible integral values of x, y satisfying 1 =< x =< 9 and 1 =< y =< 9 then number of possible ordered combinations of (x, y) are.
If y = 1, then x can have values ranging 2 to 9 so 8 possibilities.
If x = 2, then x can have values ranging 3 to 9 so 7 possibilities.
If y = 3, then x can have values ranging 6 to 9 so 4 possibilities.
If y = 4, then x can have values only 9 so 1 is possibilities.
Ramesh hears a sound of whistle after 2 sec. of whistling by Shyam and Shyam hears a sound of whistle after 3 sec. of whistling by Ramesh. If Ramesh and Shyam are in the line of flow of wind, then velocity of wind in m/s is
(Given that the speed of sound is 300 m/s)
OPtion
1) 80
2) 50
3) 40
4) 30
5) 70
6) 90
7) Wind is not blowing
8) Data are insufficient
9) 60
10)20
Solution
Ramesh hears a sound of whistle after 2 sec. of whistling by Shyam and Shyam hears a sound of whistle after 3 sec.
(greater than 2 sec.) of whistling by Ramesh. These data indicate that wind is blowing from Shyam to Ramesh
According to first condition l = (300 + x) 2,
l represents distance between them
According to second condition l = (300 - x) 3
On solving these equations, we get x = 60
The age of a man is equal the sum of ages of his 3 sons at present. What was the ratio of his age & his eldest son's age 3 year before. Given that the difference of age of his sons is 3 & age of father is 48 at present.
According to given condition
f = a+b+c
f = c-6+c-3+c (c is the age of eldest son)
f = 3c - 9
f/3 = c-3
So ratio
(f-3)/(c-3) = (f-3)/(f/3)
45/16
Option 4)
The sum of a non zero number, its square, its cube and its four power is 7380. If five power of the number is added to 7380 and divided by the number, then quotient will be?
x + x^2 + x^3 + x^4 = 7380
Add x^5 on both the side
We get
x + x^2 + x^3 + x^4 + x^5 = 7380 + x^5
Now divide by x on both the side
(x + x^2 + x^3 + x^4 + x^5)/x = (7380 + x^5)/x
1 + x + x^2 + x^3 + x^4 = (7380 + x^5)/x
1+7380 =
7381
Option 4)
Balls are arranged in rows to form an equilateral triangle. The first row consists of one ball, the second of two balls, the third of 3 balls and so on. If 456 more balls are added then all the balls can be arranged in the shape of a square and each of its sides then contains 8 balls less than the balls in each side of the triangle. Determine the initial number of balls.
Let number of balls in a side of the triangle are n
Thus total number of balls are
x = 1 + 2 + 3 +........+(n-2) + (n-1) + n (1)
or
x = n + (n-1) + (n-2) +.......+ 3 + 2 + 1 (2)
adding (1) and (2)
2x =(n+1) +(n+1) + (n+1)+.......+(n+1) +(n+1)+(n+1)
or 2x = n.(n+1)
or x =n(n+1)/2
According to given condition n(n+1)/2 + 456 = (n-8)2
On solving or checking the options we get n = 49
Thus x = 49*50/2 = 1225