The first volume of the sixth grade mathematics wide-angle problem
The big oil bottle is 4kg, and the small oil bottle 1 bottle is 0.5kg. Now suppose that all 32 bottles are small bottles, which should be 32*0.5= 16kg, but actually it is 100kg, with a difference of100-16 = 84.
So there are 24 big oil bottles and 8 small oil bottles.