Answer:
option D
Explanation:
given,
length of the pipe, L = 0.96 m
Speed of sound,v = 345 m/s
Resonating frequency when both the end is open

n is the Harmonic number
2nd overtone = 3rd harmonic
so, here n = 3
now,

f = 540 Hz
The common resonant frequency of the string and the pipe is closest to 540 Hz.
the correct answer is option D
Answer:
3200 has the fewest number of sig figs
Explanation:
sorry i was late
Potential energy which is the stored energy an object has waiting to be used
Answer:
Time taken by A and B is 1.2 hr.
Explanation:
Given that
Time taken by tank when all(A+B+C) are open = 1 hr
Time taken by tank when A+C are open = 1.5 hr
Time taken by tank when B+C are open = 2 hr
If we treat as filling of tank is a work then
Work = time x rate
Lets take work is 1 unit
1 = 1(1/a+1/b+1/c) ---------1
1 = 1.5(1/a+1/c) ----------2
1 = 2(1/b+1/c) --------3
From equation 1 and 3
1=1(1/a+1/2)
a=2
Form equation 2
1 = 1.5(1/2+1/c)
c=6
From equation 3
1 = 2(1/b+1/6)
b=3
So time taken by
A is alone to fill tank is 2 hr
B is alone to fill tank is 3 hr
C is alone to fill tank is 6 hr
So 
Time taken by A and B is 1.2 hr.