计算下面各题.(能用简算的用简算)
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/08/25 23:33:38
计算下面各题.(能用简算的用简算)
①100000÷32÷125÷25
②199999+19999+1999+199+19
③200.8×7.3-63×20.08
④888888×88888
⑤
①100000÷32÷125÷25
②199999+19999+1999+199+19
③200.8×7.3-63×20.08
④888888×88888
⑤
1 |
1×2 |
①100000÷32÷125÷25,
=100000÷(32×125×25),
=100000÷(4×8×125×25),
=100000÷[(8×125)×(4×25)],
=100000÷[1000×100],
=100000÷100000,
=1;
②199999+19999+1999+199+19,
=(199999+1)+(19999+1)+(1999+1)+(199+1)+(19+1)-5,
=200000+20000+2000+200+20-5,
=222220-5,
=222215;
③200.8×7.3-63×20.08,
=20.08×73-63×20.08,
=20.08×(73-63),
=20.08×10,
=200.8;
④888888×88888,
=888888×(80000+8000+800+80+8),
=71111040000+7111104000+711110400+71111040+7111104,
=79011476544;
⑤
1
1×2+
1
2×3+
1
3×4+…+
1
98×99+
1
99×100,
=1-
1
2+
1
2-
1
3+
1
3-
1
4+…+
1
98-
1
99+
1
99-
1
100,
=1-
1
100,
=
99
100;
⑥
382+498×381
382×498−116,
=
382+498×381
(381+1)×498−116,
=
382+498×381
381×498+498−116,
=
382+498×381
381×498+382,
=1.
=100000÷(32×125×25),
=100000÷(4×8×125×25),
=100000÷[(8×125)×(4×25)],
=100000÷[1000×100],
=100000÷100000,
=1;
②199999+19999+1999+199+19,
=(199999+1)+(19999+1)+(1999+1)+(199+1)+(19+1)-5,
=200000+20000+2000+200+20-5,
=222220-5,
=222215;
③200.8×7.3-63×20.08,
=20.08×73-63×20.08,
=20.08×(73-63),
=20.08×10,
=200.8;
④888888×88888,
=888888×(80000+8000+800+80+8),
=71111040000+7111104000+711110400+71111040+7111104,
=79011476544;
⑤
1
1×2+
1
2×3+
1
3×4+…+
1
98×99+
1
99×100,
=1-
1
2+
1
2-
1
3+
1
3-
1
4+…+
1
98-
1
99+
1
99-
1
100,
=1-
1
100,
=
99
100;
⑥
382+498×381
382×498−116,
=
382+498×381
(381+1)×498−116,
=
382+498×381
381×498+498−116,
=
382+498×381
381×498+382,
=1.