Age:
8-9 years old

Aims:
To learn another way to subtract numbers.

Introduction:
The teacher presents a method for subtracting numbers with two digits

• the minuend is placed in the top space and the subtrahend in the bottom space created by drawing a cross on the board
• the two numbers are decomposed into tens and units
• the units are written in the same spaces as the decomposed numbers
• the tens are written in the free parts of the cross, the tens in the minuend on the left and the tens in the subtrahend on the right
• the original numbers are crossed out
• the following subtractions are carried out: the number on top minus the number at the bottom and the number on the left minus the number on the right
• the results of the subtractions are added together ( if the number on the left is smaller than the number on the right the addition becomes a subtraction)

A pupil does an example on the board.

Main part:
The pupils practise the new method in class.