Tính bằng cách thuận tiện nhất :

a) 46×17+38×46+46×44+46

b) 245×687+245×313

c) 1345×765 - 345×765

d) 25×57×4

e) 50×200×25×400

a)46×17+38×46+46×44+46
= $46$×$17$+$38$×$46$+$46$×$44$+$46$x$1$
=$46$x($17$+$38$+$44$+$1$)
=$46$x$100$
=$4600$

b) $245$×$687$+$245$×$313$
= $245$ × ($687$ + $313$)
= $245 $× $1000$
= $245000$

c) $1345$×$765 $- $345$×$765$
= ($1345$ - $345$) × $765$
= $1000$ × $765$
= $765000$

d) $25$×$57$×$4$
= $100 $× $57$
= $5700$

e) $50$×$200$×$25$×$400$
= ($50$ × $200$)× ($25$ × $400$)
= $10000$ × $10000$
= $100000000$

`a) 46 xx 17 + 38 xx 46 + 46 xx 44 + 46`

`= 46 xx ( 17 + 38 + 44 + 1 ) `

`= 46 xx 100`

`= 4600`

`b) 245 xx 687 + 245 xx 313`

`= 245 xx ( 687 + 313 )`

`= 245 xx 1000`

`= 245000`

`c) 1345 xx 765 - 345 xx 765`

`= 765 xx ( 1345 - 345 )`

`= 765 xx 1000`

`= 765000`

`d) 25 xx 57 xx 4`

`= ( 25 xx 4 ) xx 57`

`= 100 xx 57`

`= 5700`

`e) 50 xx 200 xx 25 xx 400`

`= ( 50 xx 200 ) xx ( 25 xx 400 )`

`= 10000 xx 10000`

`= 100000000`

$\text{#lknhatminh0322}$