题目内容
(1)
(2)
(3)12.87+3.65+1.35
(4)74.6×19+19×25.4
(5)
(6)168.1÷(4.5×2-0.8)
解:(1)

×
=
×
×
=

=
;
(2)(
)×15
=
×15
=14;
(3)12.87+3.65+1.35
=12.87+(3.65+1.35)
=12.87+5
=17.87;
(4)74.6×19+19×25.4
=(74.6+25.4)×19
=100×19
=1900;
(5)【1-(
)】
=【1-
】×
=
×
=
;
(6)168.1÷(4.5×2-0.8)
=168.1÷8.2
=20.5;
分析:不能简算的题,要先算乘除法,再算加减法;能简算的题,运用运算定律进行简算,要有择优意识.
点评:属于数的四则运算,灵活运算.
=
=
=
(2)(
=
=14;
(3)12.87+3.65+1.35
=12.87+(3.65+1.35)
=12.87+5
=17.87;
(4)74.6×19+19×25.4
=(74.6+25.4)×19
=100×19
=1900;
(5)【1-(
=【1-
=
=
(6)168.1÷(4.5×2-0.8)
=168.1÷8.2
=20.5;
分析:不能简算的题,要先算乘除法,再算加减法;能简算的题,运用运算定律进行简算,要有择优意识.
点评:属于数的四则运算,灵活运算.
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例:
3÷3+3-3=1 33÷33=1(1)
|
① 3 3 3 3=1 |
② 3 3 3 3=2 |
|
③ 3 3 3 3=3 |
④ 3 3 3 3=4 |
|
⑤ 3 3 3 3=5 |
⑥ 3 3 3 3=6 |
|
⑦ 3 3 3 3=7 |
⑧ 3 3 3 3=8 |
|
⑨ 3 3 3 3=9 |
⑩ 3 3 3 3=10 |
(2)
|
① 3 3 3 3=1 |
② 3 3 3 3=2 |
|
③ 3 3 3 3=3 |
④ 3 3 3 3=4 |
|
⑤ 3 3 3 3=5 |
⑥ 3 3 3 3=6 |
|
⑦ 3 3 3 3=7 |
⑧ 3 3 3 3=8 |
|
⑨ 3 3 3 3=9 |
⑩ 3 3 3 3=10 |
|
① 3 3 3 3=1 |
② 3 3 3 3=2 |
|
③ 3 3 3 3=3 |
④ 3 3 3 3=4 |
|
⑤ 3 3 3 3=5 |
⑥ 3 3 3 3=6 |
|
⑦ 3 3 3 3=7 |
⑧ 3 3 3 3=8 |
|
⑨ 3 3 3 3=9 |
⑩ 3 3 3 3=10 |