Bài 1: Tính nhanh: 5+ 5 + 5 + 5+ 5 + 5 +5+ 5 + 5 +5 25 + 25 + 25 + 25 + 25 + 25 +25 + 25 45 + 45 + 45 + 45 + 15 + 15 + 15 + 15 2 + 4 + 6 + 8 + 10 + 12

0 bình luận về “Bài 1: Tính nhanh: 5+ 5 + 5 + 5+ 5 + 5 +5+ 5 + 5 +5 25 + 25 + 25 + 25 + 25 + 25 +25 + 25 45 + 45 + 45 + 45 + 15 + 15 + 15 + 15 2 + 4 + 6 + 8 + 10 + 12”

1. $5+5+5+5+5+5+5+5+5+5$

   $=5×10$

   $=50$

   $25+25+25+25+25+25+25+25$

   $=25×8$

   $=200$

   $45+45+45+45+15+15+15+15$

   $=45×4+15×4$

   $=180+60$

   $=240$

   $2+4+6+8+10+12+14+16+18$

   $=(2+18)+(4+16)+(6+14)+(8+12)+10$

   $=20+20+20+20+10$

   $=90$

   $125+125+125+125-25-25-25-25$

   $=(125-25)+(125-25)+(125-25)+(125-25)$

   $=100+100+100+100$

   $=400$

    

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2. Đáp án:

   5+ 5 + 5 + 5+ 5 + 5 +5+ 5 + 5 +5

     = 5 × 10

     = 50
   25 + 25 + 25 + 25 + 25 + 25 +25 + 25

     = (25 + 25) + (25 + 25) + (25 + 25) +(25 + 25)

     = 50 + 50 + 50 + 50 

     = 50 × 4

     = 200
   45 + 45 + 45 + 45 + 15 + 15 + 15 + 15

     = (45+15) + (45+15) + (45+15) + (45+15)

     = 60 + 60 + 60 + 60

     = 60 × 4

     = 240
   2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18

     = (2+18) + (4+16) + (6+14) + (8+12) + 10

     = 20 + 20 + 20 + 20 +10

     = 20 × 4 +10

     = 80 + 10

     = 90
   125 + 125 + 125 + 125 – 25 – 25 – 25 – 25

     = (125-25) + (125-25) + (125-25) + (125-25)

     = 100+100+100+100

     = 100 × 4

     = 400

    

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