Tính nhanh :\(\frac{32x53-21}{53x31+32}\)
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\(\frac{32.53-21}{53.31+32}=\frac{53.31+53.1-21}{53.31+32}=\frac{53.31+53-21}{53.31+32}=\frac{53.31+32}{53.31+32}=\frac{1}{1}=1\)
\(\frac{32.53-21}{53.31+32}=\frac{31.53+53-21}{53.31+32}=\frac{31.53+32}{53.31+32}=1\)
a)B = 32 x 53 - 31 =31 x 53 + 53 -31 = 31 x 53 + 22
mà 32 < 22
-> A >B
a,
ta có:
B=32*53-31
=(31+1)*53-31
=31*53+53-31
=31*53+22
suy ra B<A
b,
Ta có:
C=2000*2000
=(1990+10)*(2010-10)
=1990*2010-1990*10+2010810-10*10
=1990*2010+10*(2010-1990-10)
=1990*2010+100
suy ra C>D
53 x 31+ 32
= 1643 + 32
= 1643 + 32
= 1675
Vậy : 53 x 31+ 32 = 1675
Toán lớp 5
25.83-10>31.26+10
32.53-31<53.31+32
theo mình dấu chấm là dấu nhân đó nhé!
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{7}+...+\frac{1}{32}-\frac{1}{81}\)
\(=1-\frac{1}{81}\)
\(=\frac{80}{81}\)
18/21 +19/32 +3/21+13/32
= (18/21 + 3/21) + (19/32 + 13/32)
= 1 + 1=2
Đặt \(B=\frac{1}{1.2}+\frac{5}{2.7}+\frac{8}{7.15}+\frac{13}{15.28}+\frac{21}{28.49}+\frac{32}{49.81}\)
\(\Rightarrow B=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}+\frac{1}{28}-\frac{1}{49}+\frac{1}{49}-\frac{1}{81}\)
\(\Rightarrow B=1-\frac{1}{81}\)
\(\Rightarrow B=\frac{80}{81}\)
\(\frac{75}{100}+\frac{18}{21}+\frac{19}{32}+\frac{1}{4}+\frac{3}{21}+\frac{13}{32}\)
\(=\left(\frac{75}{100}+\frac{1}{4}\right)+\left(\frac{18}{21}+\frac{3}{21}\right)+\left(\frac{19}{32}+\frac{13}{31}\right)\)
\(=1+1+1\)
\(=3\)
75100+1821+1932+14+321+133275100+1821+1932+14+321+1332
=(75100+14)+(1821+321)+(1932+1331)=(75100+14)+(1821+321)+(1932+1331)
=1+1+1=1+1+1
=3