Answer
$91.95\%$
Work Step by Step
Number of moles of water removed:
$(1.245\ g - 0.832\ g)/18.015\ g/mol=0.0229\ mol$
Number of moles of the hydrated salt:
$0.0229\ mol/5=0.0046\ mol$
Mass fraction of the hydrated salt:
$0.0046\ mol\times 249.685\ g/mol=1.145\ g$
$1.145/1.245\times100\%=91.95\%$