Firstly we have to check how much we have to pay for one pound.
In $1.60 we can buy half pound grapes,
cost of 1 pound grapes = (1.60).(2) = $3.20
Multiply 1.60 by 2 since they have given the cost of half a pound.
How much will you buy in $64 so to do this we will divide $64 by $3.28
64/3.28 = 19.51 lbs
So in $64 we can buy 19.51 pounds of grapes or 19.5 pounds of grapes after rounding.