A. 1 hr
B. 2 hrs
C. 6 hrs
D. 8 hrs
Explanation:
Let the cistern be filled by pipe A alone in x hours.
Then, pipe B will fill it in (x + 6) hours.
1/x + 1/(x + 6) = 1/4
x2 – 2x – 24 = 0
(x – 6)(x + 4) = 0 => x = 6.
A. 15 kmph
B. 10 kmph
C. 12 kmph
D. 12.5 kmph
E. None of these
Explanation:
Let the speed of the man in still water be a kmph and let the speed of the stream be b kmph.
Now 30/(a + b) + 20/(a – b) = 4 and 45/(a + b) + 40/(a – b) = 7
Solving the equation, the speed of man in still water is 12.5 kmph.
A. 3/5
B. 5/16
C. 2/9
D. None of these
A. 9 1/4 min
B. 11 1/4 min
C. 7 1/4 min
D. 8 1/2 min
Explanation:
3/12 + x/15 = 1
x= 11 1/4
A. 15 years
B. 17 years
C. 18 years
D. 19 years
Explanation:
Sum of the ages of 14 students
= (16 * 35) – (14 * 21) = 560 – 294 = 266
Required average = (266/14) = 19 years
A. 300
B. 200
C. 400
D. 500
Explanation:
(60/100) * X + 120 = X
2X = 600
X = 300