An isotope of manganese has 25 protons and 30 neutrons. What is the mass number of this isotope?

The value of the mass number is 55.

The formula for mass number is as follows:-

Substitute 25 for number of protons and 30  for number of neutrons in the above equation as follows:-

Hence, the value of the mass number is 55.

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55

Explanation:

mass number is neutron + proton

25+30

=55

note that the atomic number is =proton

the answer is b & c i believe : )