1 astronomical unit = 149597870700m
Enrico should divide distance in meters with this number.
Explanation:
Given that,
Terminal voltage = 3.200 V
Internal resistance 
(a). We need to calculate the current
Using rule of loop


Where, E = emf
R = resistance
r = internal resistance
Put the value into the formula


(b). We need to calculate the terminal voltage
Using formula of terminal voltage

Where, V = terminal voltage
I = current
r = internal resistance
Put the value into the formula


(c). We need to calculate the ratio of the terminal voltage of voltmeter equal to emf


Hence, This is the required solution.
Answer:
1) The speed of sound increases
2) 440 Hz
3) 29°C
4) 17°C
5) 434 Hz
6) 12 m/s
7) 17.3 m
Explanation:
1) The speed of sound increases
2) V = f×λ
f = V/λ = 343/0.78 = 439.744 ≈ 440 Hz
3) V = f×λ
512 × 0.68 = 348.16 m/s
348.16 - 331 = 17.16
T = 17.16/0.6 = 28.6 ≈ 29°C
4) Increase in speed = 350 - 340 = 10
Increase in temperature = 10/0.6 = 16.67° ≈ 17°C
5) f = V/λ = 343/0.79 = 434 Hz
6) 331 + 0.6×30 - (331 × 0.6 ×10) = 12 m/s
7) V = 331 + 0.6×25 = 346m/s
λ = 346/20 = 17.3 m