The height at which the atmosphere ceases to exist is about 80km. If the atmospheric…

The height at which the atmosphere ceases to exist is about 80km. If the atmospheric pressure on the ground level is 760mmHg, the pressure at a height of 20km above the ground level is

Correct Answer: Option B

Explanation

(p – 760)/(0 – 760) = (h – 0)/(80 – 0)
∴ (p – 760)/-760 = (20 – 0)/80
80(p-760) = -760(20-0)
∴80p – 60800 = -15200
80p = 60800 – 15200
80p = 45600
∴ p = 45600/80
p = 570mmHg