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用简便方法计算.(1)72+186+214(2)7825+9+341(3)804+1789(4)1997+5803+5003+197(5)158+36+42+264(6)386+69+214+531(7)11+14+17+…+68(8)2+6+10+…+62(9)199999+19999+1999+199+19.
题目详情
| 用简便方法计算. (1)72+186+214 | (2)7825+9+341 | (3)804+1789 |
| (4)1997+5803+5003+197 | (5)158+36+42+264 | (6)386+69+214+531 |
| (7)11+14+17+…+68 | (8)2+6+10+…+62 | (9)199999+19999+1999+199+19. |
▼优质解答
答案和解析
(1)72+186+214,
=72+(186+214),
=72+400,
=472;
(2)7825+9+341,
=7825+(9+341),
=7825+350,
=8175;
(3)804+1789,
=800+1789+4,
=2593;
(4)1997+5803+5003+197,
=(1997+5003)+(5803+197),
=7000+6000,
=13000;
(5)158+36+42+264,
=(158+42)+(36+264),
=200+300,
=500;
(6)386+69+214+531,
=(386+214)+(69+531),
=600+600,
=1200;
(7)11+14+17+…+68,
=[(11+68)×20]÷2,
=[79×20]÷2,
=790;
(9)199999+19999+1999+199+19,
=200000+20000+2000+200+20-4,
=222216.
=72+(186+214),
=72+400,
=472;
(2)7825+9+341,
=7825+(9+341),
=7825+350,
=8175;
(3)804+1789,
=800+1789+4,
=2593;
(4)1997+5803+5003+197,
=(1997+5003)+(5803+197),
=7000+6000,
=13000;
(5)158+36+42+264,
=(158+42)+(36+264),
=200+300,
=500;
(6)386+69+214+531,
=(386+214)+(69+531),
=600+600,
=1200;
(7)11+14+17+…+68,
=[(11+68)×20]÷2,
=[79×20]÷2,
=790;
(9)199999+19999+1999+199+19,
=200000+20000+2000+200+20-4,
=222216.
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