выполни вычисления по образцу 470 + 80 = 470 + (30 + 50) = (470 + 30) + 50 = 500 + 50 = 550
560 – 90 = 560 – (60 + 30) = (560 – 60) – 30 = 500 – 30 = 470 360 + 50 = 360 + (
+
) = (360 +
) +
=
+
=

290 + 70 = 290 + (
+
) = (290 +
) +
=
+
=

830 – 80 = 830 – (
+
) = (830 –
) –
=
–
=

420 – 60 = 420 – (
+
) = (420 –
) –
=
–
=
К списку заданий

290+70=290+(30+40)=(290+30)+40=320+40=360

830 -80=830-(40+40)=(830-40)-40=790-40=750

420-60=420-(30+30)=(420-30)-30=390-30=360.

360+50=360+(40+10)=(360+40)+10=400+10=410

290+70=290+(10+60)=(290+10)+60=300+60=360

830-80=830-(30+50)=(830-30)-50=800-50=750

420-60=420-(20+40)=(420-20)-40=400-40=360