中一數學題!!!(有好多,唔該幫下手,不過要有過程)~~~

2008-02-05 7:23 am

1a 2乘{80除[(7-3)乘5]-5} . 1b (8-4)-6除(5-2) 1c 16除[(1-2+3)乘4] 1d {2+[(13-5)乘2]}乘10
2 用+ - 乘除或( )將下列各題寫成算式,並計算結果
a 20減去5,然後乘7 b 30除15的商除去10 c 從65減去當30減21所得的差 d 9乘以5加4所得的和
3a. 3+1/3-3/4 b 2又2/5-5又1/7+9又7/9 c 2/3+11/12乘4/5 d 5/6乘(1-4/5)除(21/2)
4 求下列的值 a.85的25% b.150km的170% c.x的45%是10 d. y的120%是186 e. 100cm是n cm的40% f. 00mL是k mL 的150%
5.已知某數列通項是-2(-1)/3,求該數列的首5項.
冇啦,唔該!!謝謝~~~!!!!

回答 (1)

用戶159453

2008-02-05 3:36 pm

✔ 最佳答案

Note** 除in here will become: /
乘in here will become: x
1a. 2x{80/[(7-3)x5]-5}
=2x{80/20-5}
=2x(-1)
=-2
1b. (8-4)-6/(5-2)
=4-6/3
=4-2
=2
1c. 16/[(1-2+3)x4]
=16/[2x4]
=16/8
=2
1d. {2+[(13-5)x2]}x10
={2+[8x2]}x10
={2+16}x10
=18x10
=180
2a. (20-5)x7
=4x7
=28
2b. (30/15)/10
=2/10
=0.2
2c. 65-(30-21)
=65-9
=56
2d. 9x(5+4)
=9x9
=81
3a. 3+1/3-3/4
=3/3+1/3-3/4
=12/12+4/12-9/12(通分母)
=16/12-9/12
=7/12
3b. 2又2/5-5又1/7+9又7/9
=12/5-36/7+88/9(化作假分數)
=756/315-1620/315+3080/315(通分母)
=756/315+3080/315-1620/315
=3836/315-1620/315
=2216/315
=7
3c. 2/3+11/12x4/5
=40/60+55/60x48/60(通分母)
=40/60+11/15
=40/60+44/60
=84/60
=7/5 or 1.4
3d. 5/6x(1-4/5)/(21/2)
=5/6x(1/5)/(21/2) **(I use () here to make it clearly)
=5/6x1/5x2/21
=1/6x2/21
=1/63
4a. 85x25%
=21.3
4b. 150x170%
=225km
4c. x的45%=10
x=10/45%
x=22.2
4d. y的120%=186
y=186/120%
y=155
4e. nx40%=100
n=100/40%
n=250
4f. it is not clear, i don't know how many ml are there..
5. i am not sure with this, sorry about that!!=[

Hope my opinion can help!!

參考: myself=]

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