Tính nhanh
a) 12,7 + 12,7 + 12,7 + 12,7 x 8 – 12,7
b) 81,3 x 99 + 82 – 0,7
c) (100 + 42) x 42 + (200 – 58) x 58
d) 17,8 x 99 + 17 + 0,8
e) 103,7 x 101 – 103 – 0,7
g) 124 x 76 + 12 x 248
h) 12,48 x 3,47 – 3,47 x 2,48
i) 128 x 68 + 16 x 256
Tính nhanh
a) 12,7 + 12,7 + 12,7 + 12,7 x 8 – 12,7
b) 81,3 x 99 + 82 – 0,7
c) (100 + 42) x 42 + (200 – 58) x 58
d) 17,8 x 99 + 17 + 0,8
e) 103,7 x 101 – 103 – 0,7
g) 124 x 76 + 12 x 248
h) 12,48 x 3,47 – 3,47 x 2,48
i) 128 x 68 + 16 x 256
Đáp án + Giải thích các bước giải:
Ta có :
`a,12,7+12,7+12,7+12,7.8-12,7`
`=12,7(1+1+1+8-1)`
`=12,7.10`
`=127`
`————`
`b,81,3.99+82-0,7`
`=81,3.99+(82-0,7)`
`=81,3.99+81,3`
`=81,3(99+1)`
`=81,3.100`
`=8130`
`————-`
`c,(100+42).42+(200-58).58`
`=142.42+142.58`
`=142(42+58)`
`=142.100`
`=14200`
`————–`
`d,17,8.99+17+0,8`
`=17,8.99+(17+0,8)`
`=17,8.99+17,8`
`=17,8(99+1)`
`=17,8.100`
`=1780`
`————–`
`e,103,7.101-103-0,7`
`=103,7.101-(103+0,7)`
`=103,7.101-103,7`
`=103,7(101-1)`
`=103,7.100`
`=10370`
`————-`
`g,124.76+12.248`
`=124.76+12.2.124`
`=124.76+24.124`
`=124(76+24)`
`=124.100`
`=12400`
`————-`
`h,12,48.3,47-3,47.2,48`
`=3,47(12,48-2,48)`
`=3,47.10`
`=34,7`
`————-`
`i,128.68+16.256`
`=128.68+16.2.128`
`=128.68+32.128`
`=128(68+32)`
`=128.100`
`=12800`
a)`12,7+12,7+12,7+12,7×8-12,7`
`=12,7×(1+1+1+8-1)`
`=12,7×10`
`=127`
b)` 81,3×99+82-0,7`
`=81,3×99+81,3`
`=81,3×(99+1)`
`=81,3×100`
`=8130`
c)`(100+42)×42+(200-58)×58`
`=142×42+142×58`
`=142×(42+58)`
`=142×100`
`=14200`
d)` 17,8×99+17+0,8`
`=17,8×99+17,8`
`=17,8×(99+1)`
`=17,8×100`
`=1780`
e)`124×76+12×248`
`=124×76+24×124`
`=124×(76+24)`
`=124×100`
`=12400`
h)`12,48×3,47-3,47×2,48`
`=3,47×(12,48-2,48)`
`=3,47×10`
`=34,7`
i)`128×68+16×256`
`=128×68+32×128`
`=128×(68+32)`
`=128×100`
`=12800`