Let the number that should be added in 823 be x to get 1256
⇒ 823+x=1256
Now, we have :
823+x=1256
Mixed Fraction=Integral part×Denominator +NumeratorDenominator
We will use the above formula to convert the mixed fraction into improper fraction.
8×3+23+x=12×6+56
⇒ 24+23+x=72+56
⇒ 263+x=776
⇒ x=776−263
x=776−26×23×2
[LCM of (6,3)=6]
x=776−526=77−526=256
Hence, 256 or 416 should be added to 823 to get 1256