1.Tính nhanh
a. 91.25 -91 . 13 – 91.12
b.236 : 3 + 64 : 3
c. 47 . 8 – 27 .9 + 47 . 12 – 27 -11
d. 375 : 25 – 125 : 25
2. tìm x
a,(x-25)-175=0
b,485-(6x=60)=5
c,315+(135-x)=450
d,346+(210-x)=556
1.Tính nhanh a. 91.25 -91 . 13 – 91.12 b.236 : 3 + 64 : 3 c. 47 . 8 – 27 .9 + 47 . 12 – 27 -11 d. 375 : 25 – 125 : 25 2. tìm x a,(x-25)-175=0 b,485-(
By Samantha
giải
a. 91.25 -91 . 13 – 91.12
= 91 (25 – 13 – 12)
= 91 . 0
= 0
b.236 : 3 + 64 : 3
= (236 + 64) : 3
= 300 : 3
=> 100
c. 47 . 8 – 27 .9 + 47 . 12 – 27 . 11
= 47 (8 + 12) – 27 (9 + 11)
= 47 . 20 – 27 . 20
= 20 . (47 – 27)
= 20 . 20
= 400
d. 375 : 25 – 125 : 25
= (375 – 125) : 25
= 250 : 25
= 10
2. tìm x
a,(x – 25) – 175 = 0
=> x – 25 = 175
=> x = 200
b,485 – (6x + 60) = 5
=> 6x + 60 = 480
=> 6x = 420
=> x = 70
c,315 + (135 – x)=450
=> 135-x = 135
=> x = 0
d,346 + (210 – x) = 556
=> 210 – x = 210
=> x = 0
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