The initial value of P*V = 0.100*150 atm-m³
Each balloon has a volume of (4/3)*π*r³ and N balloons have a volume of N*(4/3)*π*r³
When all the balloons are inflated, the pressure in the tank is the same as the pressure in the balloons, so the final value of P*V is
1.20*[N*(4/3)*π*r³ + 0.100]
0.100*150 = 1.20*[N*(4/3)*π*r³ + 0.100] solve for N:
15/1.2 = N*(4/3)*π*r³ + 0.100
12.5 - 0.100 = N*(4/3)*π*0.150³
12.4 = N*0.01414
N = 877
