Question

tính nhanh

\(5\times7\times77-7\times60+49\times25-15\times42\)

các bn giúp mk nhanh nha

 

Answer 1

5 x 7 x 77 - 7 x 60 + 49 x 25 - 15 x 42

= (5 x 77) x 7 - 7 x 60 + 7 x 7 x 25 - 15 x 6 x 7

= 385 x 7 - 7 x 60 + 7 x (7 x 25) - 90 x 7

= 385 x 7 - 7 x 60 + 7 x 175 - 90 x 7

= 7 x (385 - 60 + 175 - 90)

= 7 x 410

= 2870

Answer 2

= 7 x 5 x 77 - 7 x 60 + 7 x 7 x 25 - 7 x 6 x 15

= 7 x 5 x 77 - 7 x 5 x 12 + 7 x 5 x 5 x 7 - 7 x 5 x 3 x 6

= 7 x 5 x ( 77 - 12 + 5 x 7 - 3 x 6 )

= 7 x 5 x ( 77 - 12 + 35 - 36 )

= 7 x 5 x ( 65 + 35 - 36 )

= 7 x 5 x ( 100 - 36 )

= 7 x 5 x 64

= 2240