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Bài làm
124 x 76 + 12 x 248
= 124 x 76 + 24 x 124
= 124 x ( 76 + 24 )
= 124 x 100
= 12400
Bài làm
128 x 68 + 16 x 256
= 128 x 68 + 32 x 128
= 128 x ( 68 + 32 )
= 128 x 100
\(\frac{5}{2}+\frac{5}{4}+\frac{5}{8}+\frac{5}{16}+\frac{5}{32}+\frac{5}{64}+\frac{5}{128}+\frac{5}{256}\)
\(\Rightarrow5-\frac{5}{2}+\frac{5}{2}-\frac{5}{4}+\frac{5}{4}-\frac{5}{8}+\frac{5}{8}-\frac{5}{16}+...+\frac{5}{128}-\frac{5}{256}\)
\(\Rightarrow5-\frac{5}{256}\)
\(\Rightarrow\frac{1275}{256}\)
Ta có 5/2 + 5/4 + 5/8 + 5/16 + 5/32 + 5/64 + 5/128 + 5/256
= 5- 5/2 + 5/2 - 5/4 + 5/4 - 5/8 + 5/8 - 5/16 + 5/16 - 5/32 + 5/32 - 5/64 + 5/64 - 5/128 + 5/128 - 5/256
= 5-5/256
= 1275/256
b ) Đặt \(A=\frac{5}{1.3}+\frac{5}{3.5}+\frac{5}{5.7}+...+\frac{5}{101.103}\)
\(\Rightarrow A=\frac{5}{2}\left(\frac{5}{1}-\frac{5}{3}+\frac{5}{3}-\frac{5}{5}+....+\frac{5}{101}-\frac{5}{103}\right)\)
\(\Rightarrow A=\frac{5}{2}\left(5-\frac{5}{103}\right)\)
20,21 x 36 + 63 x 20,21 + 20,21
= 20,21 x 36 + 63 x 20,21 + 20,21 x 1
= 20,21 x ( 36 + 63 + 1)
= 20,21 x 100
= 2 021
a ) 2 x 3 x 4 x 8 x 50 x 25 x 125
= 3 x 2 x 50 x 4 x 25 x 8 x 125
= 3 x ( 2 x 50 ) x ( 4 x 25 ) x ( 8 x 125 )
= 3 x 100 x 100 x 1000
= 30000000
b ) 45 x 128 - 90 x 64
= 45 x ( 2 x 64 ) - 90 x 64
= ( 45 x 2 ) x 64 - 90 x 64
= 90 x 64 - 90 x 64
= 0
a) = (2.50).(4.25).(8.125).3=100.100.1000.3=30000000
b)45.128-90.64=45.128-45.2.64
=45.128-45.128
=0
2008 \(\times\) 0,25 \(\times\) 0,125 \(\times\) 128
= 2008 \(\times\) 0,25 \(\times\) 0,125 \(\times\)4 \(\times\) 8 \(\times\) 4
= 2008 \(\times\) ( 0,25 \(\times\) 4) \(\times\) ( 0,125 \(\times\)8) \(\times\) 4
= 2008 \(\times\) 1 \(\times\)1 \(\times\) 4
= 2008 \(\times\) 4
= 8032
2008 ×× 0,25 ×× 0,125 ×× 128
= 2008 ×× 0,25 ×× 0,125 ××4 ×× 8 ×× 4
= 2008 ×× ( 0,25 ×× 4) ×× ( 0,125 ××8) ×× 4
= 2008 ×× 1 ××1 ×× 4
= 2008 ×× 4
= 8032
14,35 × 63 + 14,35 × 36 + 14,35
= 14,35 x 63 + 14,35 x 36 + 14,35 x 1
= 14,35 x ( 63 + 36 + 1 )
= 14,56 x 100
= 1456
\(14,35\times63+14,35\times36+14,35\)
\(=14,35\times\left(63+36+1\right)\)
\(=14,35\times100\)
\(=1435\)
a) 1245 + 696 + 755 = 2696
b) 128 × 36 + 128 × 63 + 128
= 128 x (36 + 63 + 1)
= 128 x 100
= 12800