m₁ = atomic mass of first isotope = 35.0 amu
p₁ = percentage of first isotope = 75.53% = 75.53/100 = 0.7553
m₂ = atomic mass of second isotope = 35.0 amu
p₂ = percentage of second isotope = 24.47% = 24.47/100 = 0.2447
m = average atomic of chlorine
average atomic of chlorine is given as
m = (m₁ p₁ + m₂ p₂)
inserting the above values in the equation
m = ((35.0) (0.7553) + (37) (0.2447))
m = 35.5 amu
