5,4:0,4*1420+4,5*780*3
3+6+9+12+15+18+21+24+27
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![](https://rs.olm.vn/images/avt/0.png?1311)
Đặt
- 5,4:0,4 × 1420 + 4,5 × 780 × 3
= 13,5 × 1420 + 13,5 × 780
= 13,5 × 1420 + 780
= 13,5 × 2200
= 29700
- 3 + 6 + 9 + 12 + 15 + 18 + 21 + 24 + 27
= 3 + 27 + 6 + 24 + 9 + 21 + 12 + 18 + 15
= 30 + 30 + 30 + 30 + 15
= 30 × 4 + 15
= 120 + 15
= 135
\(\Rightarrow\)\(\frac{29700}{135}\)
\(\frac{\text{5,4:0,4x1420+4,5x780x3}}{3+6+9+12+15+18+21+24+27}\)=220
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(=\frac{135\cdot142+45\cdot78\cdot3}{3\left(1+2+3+...+8+9\right)}=\frac{3\cdot45\left(142+78\right)}{3\cdot\left(\frac{9\cdot10}{2}\right)}=220\)
![](https://rs.olm.vn/images/avt/0.png?1311)
cau 1 sai de
cau 2 :
3+6+9+12+15+18+21+24+27= (3+27)+(6+34)+(9+21)+(12+18)+15= 30+30+30+30+15=135
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{5,4:0,4\times1420+4,5\times780\times3}{3+6+9+12+15+18+21+24+27}\)
\(=\frac{13,5\times1420+13,5\times780}{\left(3+27\right)+\left(6+24\right)+\left(9+21\right)+\left(12+18\right)+15}\)
\(=\frac{13,5\times\left(1420+780\right)}{30+30+30+30+15}\)
\(=\frac{13,5\times2200}{135}\)
\(=\frac{29700}{135}\)
\(=220\)
![](https://rs.olm.vn/images/avt/0.png?1311)
A = 135 × 1420 + 4 , 5 × 780 × 3 3 + 6 + 9 + . . . + 24 + 27 = 135 × 1420 + 13 , 5 × 780 3 + 7 + 6 + 24 + 9 + 21 + 21 + 18 + 15 = 135 × 142 + 78 30 × 4 + 15 = 135 × 220 135 = 220
Vậy A = 220
\(5,4:0,4\times1420+4,5\times780\times3\)
\(=13,5\times1420+13,5\times780\)
\(=13,5\times\left(1420+780\right)\)
\(=13,5\times2200\)
\(=29700\)
\(3+6+9+12+15+18+21+24+27\)
\(=\left(3+27\right)+\left(6+24\right)+\left(9+21\right)+\left(12+18\right)+15\)
\(=30+30+30+30+15\)
\(=30\times4+15\)
\(=120+15\)
\(=135\)