口算50×5=49+35=21×4=900×9=3×13=63×0=110×6=80-54=71×2≈49×3≈102×6≈198×5≈39+49=45+15=910-310=1-13=37+47=56-36=1-910=1-14=

Question

口算

50×5=	49+35=	21×4=	900×9=
3×13=	63×0=	110×6=	80-54=
71×2≈	49×3≈	102×6≈	198×5≈
(3)/(9)+(4)/(9)=	(4)/(5)+(1)/(5)=	(9)/(10)-(3)/(10)=	1-(1)/(3)=
(3)/(7)+(4)/(7)=	(5)/(6)-(3)/(6)=	1-(9)/(10)=	1-(1)/(4)=

Answer 1

50×5=250	49+35=84	21×4=84	900×9=8100
3×13=39	63×0=0	110×6=660	80-54=26
71×2≈140	49×3≈150	102×6≈600	198×5≈1000
(3)/(9)+(4)/(9)=(7)/(9)	(4)/(5)+(1)/(5)=1	(9)/(10)-(3)/(10)=(3)/(5)	1-(1)/(3)=(2)/(3)
(3)/(7)+(4)/(7)=1	(5)/(6)-(3)/(6)=(1)/(3)	1-(9)/(10)=(1)/(10)	1-(1)/(4)=(3)/(4)