解:(1)4x-15×
=54,
4x-10=54,
4x-10+10=54+10,
4x=64,
4x÷4=64÷4,
x=16;
(2)8.1:x=1
:3
,
1
x=8.1×3
,
x×
=
×
×
,
x=21
;
(3)
÷
+
÷25%,
=
×4+
÷
,
=
×4+
×4,
=(
+
)×4,
=1×4,
=4;
(4)8
×2.9+2
×1
,
=
×
+
×
,
=(
+
)×
,
=10×
,
=29;
(5)
÷[
-(
-
)],
=
÷[
+
-
],
=
÷[
-
],
=
÷
,
=
×
,
=
;
(6)[8.15-(0.2+
)×
]÷0.01,
=[8.15-(
+
)×
]÷0.01,
=[8.15-
×
]÷0.01,
=[8.15-0.2]÷0.01,
=7.95÷0.01,
=795.
分析:(1)先求出15×
=10,根據(jù)等式的性質(zhì),兩邊同加上10,再同除以4即可;
(2)先根據(jù)比例的性質(zhì)改寫成1
x=8.1×3
,再根據(jù)等式的性質(zhì),兩邊同乘
即可;
(3)把原式變?yōu)?img class='latex' src='http://thumb.zyjl.cn/pic5/latex/729.png' />×4+
×4,運(yùn)用乘法分配律的逆運(yùn)算簡(jiǎn)算;
(4)把2.9化為分?jǐn)?shù),原式變?yōu)?img class='latex' src='http://thumb.zyjl.cn/pic5/latex/218296.png' />×
+
×
,運(yùn)用乘法分配律的逆運(yùn)算簡(jiǎn)算;
(5)中括號(hào)內(nèi)運(yùn)用減法的性質(zhì)簡(jiǎn)算,最后算括號(hào)外的除法;
(6)先算小括號(hào)內(nèi)的加法,再算小括號(hào)外的乘法,然后算中括號(hào)內(nèi)的減法,最后算中括號(hào)外的除法.
點(diǎn)評(píng):此題考查了解方程以及四則混合運(yùn)算的能力.在解方程時(shí)應(yīng)根據(jù)等式的性質(zhì),同時(shí)注意等號(hào)上下要對(duì)齊;在做四則運(yùn)算題時(shí),應(yīng)注意運(yùn)算順序,以及運(yùn)用運(yùn)算定律或性質(zhì)簡(jiǎn)算.