There is no such thing as carelessness, mainly doing less.

Few children count 1+ 1 as 2, because 1+ 1 can't be wrong.

Try not to be so careless in front of children in the future. They will use this as an excuse for miscalculation.

Let me give you an example. I have seen several children in grades 3-4 count with their fingers, but when they count vertically, they don't know how to carry and align. The vertical form of multiplication is confused with the vertical form of addition.

Some children miscalculate, but they really don't, not sloppy. However, this is a stage. I can basically calculate in grades 5-6, but in grades 3-4, because I don't practice much (because I can't make mistakes), my calculation ability will be relatively lacking.

Now the fourth grade should teach simple operation. Some children can't figure out the essence of simple operation for a while.

take for example

14x 15+86x 15 =( 14+86)x 15

102x25 = (100+2) 25 = 100 x25+2x25 (some children will write100x25+2 in this step.