The number of 235U atoms in 47 g is determined using Avogadro's number.
Molar mass of 235U is 235 g/mol, so the number of moles is n=47/235 mol.
The total number of atoms is N=(47/235)×6×1023.
Since each fission releases 190 MeV, the total energy released is:
Etotal=N×190=23547×6×1023×190=23547×6×190×1023 MeV.
Calculating the numerator: 47×6×190=282×190=53580.
Therefore: Etotal=23553580×1023=228×1023 MeV, giving α=228.