Because there is no basket for the first weighing10kg,

Later, there was a basket of 10.55 kg.

Explain that a 0.5 kg basket is 0.55 kg.

Now 10 kg is equivalent to the original.

10 ÷ 0.55× 0.5 = 9 and 1 1% 1 (kg)

So it's about 1 kg.