human
Recognise and use efficient strategies for mental subtraction Tom and Katie are discussing mental addition and subtraction strategies.

Tom says a good way to add \( 9 \) is to add \( 10 \) and then subtract \( 1 \).

Katie says a good way to subtract \( 9 \) is to subtract \( 10 \) and then subtract \( 1 \).

Who is correct? Neither is correct
gpt
Does not understand the effect of consecutive operations