Approaches and methodologies
 

Rounding strategy

Numbers can be rounded in many different ways. The choice of rounding process will produce different but reasonable results, and this can be refined according to the child’s ability to compute mentally. It is necessary to give children plenty of mental practice
with this method and demonstrate how it can be refined by choosing closer rounding factors. Using this strategy can generate plenty of discussion about why one child’s answer is different from that of another.

37 x 59: in this case it would be best to round both numbers up:
40 x 60 = 2400

51 x 22: here we would round both numbers down to 50 and 20:
50 x 20 = 1000

24 x 65: they are both close to the middle so you can try rounding one
down (20) and one up (70):
20 x 70 = 1400

Rounding can be used with the four operations but is very useful in division. In division it is often better to round up:

419 ÷ 65 could be rounded to
420 ÷ 70.