(a) how much helium (density 0.18 kg/m3) is needed to lift a balloon carrying two people, if the total mass of people, basket, and balloon (but not gas) is 280 kg?
(b) repeat for a hot-air balloon whose air density is 10% less than that of the surrounding atmosphere.

(a) 1555.6m^3

(b) 17284m^3

Explanation:

Density of helium=0.18kg/m^3, density of hot-air balloon=0.18-(0.1×0.18)=0.18-0.018=0.162kg/m^3, total mass of people, basket and balloon=280kg

(a) volume = mass/density=280/0.18=1555.6m^3

(b) volume = mass/density = 280/0.162= 1728.4m^3

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures