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231 x 87 + 32 x 231 - 19 x 231
= 231 x (87 + 32 - 19)
= 231 x 100
= 23100
![](https://rs.olm.vn/images/avt/0.png?1311)
b) 168 + 2080 + 32= (168 + 32) + 2080
= 200 + 2080 = 2280
87 + 94 + 13 + 6= ( 87 + 13) + (94 +6)
= 100 + 100
121 + 85 + 115 +469= (121 + 469) + ( 85 + 115)
= 590 + 200 = 790.
![](https://rs.olm.vn/images/avt/0.png?1311)
a= 257 x (87+23)
=257 x 100
=25700
b=712 x (25+74)+752
=75200
c=94100
Chuẩn luôn rồi
Học tốt
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1, 2x30+30+5x30+60=30x(2+1+5)+60=30x8+60=240+60=300
2,3059-213+214-87=(3059-87)+(214-213)=2972+1=2973
nha
1. 2 × 30 + 30 + 5 × 30 + 60
= 2 × 30 + 30 × 1 + 5 × 30 + 30 × 2
= 30 × ( 2 + 1 + 5 + 2 )
= 30 × 10
= 300
2. 3059 - 213 + 214 - 87
= ( 3059 - 87 ) + ( 214 - 213 )
= 2972 + 1
= 2973
Cbht
![](https://rs.olm.vn/images/avt/0.png?1311)
168 + 2080+ 32
= ( 168 + 32 ) + 2080
= 200 + 2080
= 2280.
87 + 94 + 13 + 6
= ( 87 + 13 ) + ( 94 + 6 )
= 100 + 100
= 200.
121 + 85 + 115 + 469
= ( 121 + 469 ) + ( 85 + 115 )
= 590 + 200
= 790.
a, 168+2080+32
=(168+32)+2080
=200+2080
=2280
b,87+94+13+6
=(87+13)+(94+6)
=100+100
=200
c,121+85+115+469
=(121+469)+(85+115)
=590+200
=790
![](https://rs.olm.vn/images/avt/0.png?1311)
a) Ta có:
\(\frac{19}{15}\)= 1+ \(\frac{4}{15}\).
\(\frac{15}{11}\)= 1+ \(\frac{4}{11}\).
Vì \(\frac{4}{15}\)< \(\frac{4}{11}\).
=> 1+ \(\frac{4}{15}\)< 1+ \(\frac{4}{11}\).
=> \(\frac{19}{15}\)< \(\frac{15}{11}\).
Ta có 87 x 1017 – 17 x 87 = 87 x ( 1017 – 17) = 87 x 1000 = 87000