b) 238 + 106
(238+106):2=344:2=172
(238+106):2=238:2+106:2=119+53=172
(238+106)×4=344×4=1 376
(238+106)×4=238×4+106×4=952+424=1 376
c) 1 000 + 500
(1 000+500):2=1 500:2=750
(1 000+500):2=1 000:2+500:2=500+250=750
(1 000+500)×4=1 500×4=6 000
(1 000+500)×4=1 000×4+500×4=4 000+2000
= 6 000