Assume that the fruit seller initially had 100 apples
He sell 40% of them = 40 apples
Left out apples = (100 – 40)
= 60
In initial amount of apples if 60 of them are remaining = 100
In initial amount of apples if 1 of them is remaining = 100/60
In initial amount of apples if 420 of them are remaining = (100/60) x 420
We get,
= 100 x 7
= 700
Hence, the fruit seller had 700 apples