30×39= 30\times39= 30×39=
To solving easier, we break down 39 into more convenient numbers, preferably round ones.
We obtain:
30×(40−1)= 30\times(40-1)= 30×(40−1)=
We multiply 30 by each of the terms in parentheses:
(30×40)−(30×1)= (30\times40)-(30\times1)= (30×40)−(30×1)=
We solve the exercises in parentheses and obtain:
1,200−30=1,170 1,200-30=1,170 1,200−30=1,170
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