1A.若20x(1+r%)=26，求r。
1B.若30x(1-r%)=28.2，求r。
2.小樹苗原來高h cm,一個月後高度增加了28%達到44.8cm，求h的值。
3.水池原來水深dcm。如果水深減少了35%後,變成了1.82m,求d的值。
4.一個家庭某月的開支為:交通費1800元，食物2500元，雜項1700元。求交通費佔該月開支的百分數。
5.圍棋班上月有男學員30名和女學員20名。如果本月男學員的人數減少r%而女學員人數增加r%，則男女學員的人數剛好相等，求r。
數學問題(2)急!
2007-09-05 7:55 am
回答 (5)
2007-09-05 8:19 am
✔ 最佳答案
1A. (1+r%)=26/20=1.31+r% = 1.3
r% = 0.3
r = 30
1B. 30x(1-r%)=28.2
(1-r%)=28.2/30
1-r% = 0.94
r=6
2) hx(1+28%) = 44.8
h = 35
3. dx(1-35%) =1.82
d= 2.8
4. 1800/(1800+2500+1700)
= 1800 /6000
= 30%
5. 30x(1-r%) = 20x(1+r%)
30 - 30r% = 20 +20r%
10 = 50r%
0.2=r%
r = 20
2007-09-05 5:12 pm
1A)20x(1+r%)=26
26/20=1+r%
1.3=1+r%
r%=0.3
r=30
1B)30x(1-r%)=28.2
1-r%=28.2/30
1-r%=0.94
r%=1-0.94
r%=0.06
r=6
2)hx(1+28%)=44.8
h=44.8/1.28
h=35
3)dx(1-35%)=1.82
d=1.82/0.65
d=2.8
4)1800/(1800+2500+1700)x100%
=1800/6000x100%
=30%
5)30x(1-r%)=20x(1+r%)
30-30(r%)=20+20(r%)
10=50(r%)
r%=0.2
r=20
26/20=1+r%
1.3=1+r%
r%=0.3
r=30
1B)30x(1-r%)=28.2
1-r%=28.2/30
1-r%=0.94
r%=1-0.94
r%=0.06
r=6
2)hx(1+28%)=44.8
h=44.8/1.28
h=35
3)dx(1-35%)=1.82
d=1.82/0.65
d=2.8
4)1800/(1800+2500+1700)x100%
=1800/6000x100%
=30%
5)30x(1-r%)=20x(1+r%)
30-30(r%)=20+20(r%)
10=50(r%)
r%=0.2
r=20
2007-09-05 8:41 am
1a) 20x(1+r%)=26，求r。
1+r%=26÷20
1+r%=1.3
r%=1.3-1 = 1
1B.30x(1-r%)=28.2，求r。
1-r%=28.2÷30
1-r%=0.94
1=0.94+r%
1-0.94=r%
0.06=r
2. hX(1+28%) = 44.8
h x 1.28% = 44.8
h = 44.80÷1.28
h = 35
3. dx(1-35%) = 1.82
d x 0.65= 1.82
d = 1.82÷0.65
d = 2.8
4. 1800 + 2500 + 1700 = 6000
6000 ÷ 1800 = 0.3 x 100%
= 30%
5. 30x(1-r%) = 20 x (1+r%)
30÷20x(1-r%) = 1+r%
1.5x (1-r%) = 1+r%
1.5-1.5r%-1 =r%
0.5=r% + 1.5r%
0.5=2.5r%
0.5÷2.5=r%
0.2x100 = r
20% = r
1+r%=26÷20
1+r%=1.3
r%=1.3-1 = 1
1B.30x(1-r%)=28.2，求r。
1-r%=28.2÷30
1-r%=0.94
1=0.94+r%
1-0.94=r%
0.06=r
2. hX(1+28%) = 44.8
h x 1.28% = 44.8
h = 44.80÷1.28
h = 35
3. dx(1-35%) = 1.82
d x 0.65= 1.82
d = 1.82÷0.65
d = 2.8
4. 1800 + 2500 + 1700 = 6000
6000 ÷ 1800 = 0.3 x 100%
= 30%
5. 30x(1-r%) = 20 x (1+r%)
30÷20x(1-r%) = 1+r%
1.5x (1-r%) = 1+r%
1.5-1.5r%-1 =r%
0.5=r% + 1.5r%
0.5=2.5r%
0.5÷2.5=r%
0.2x100 = r
20% = r
2007-09-05 8:20 am
(1a) 20 (1+r%) = 26
1+r% = 26/20 = 1.3
r/100 = 0.3
r =30
(1b) 30 ( 1-r%) = 28.2
1-r% = 0.94
r/100 = 0.06
r = 6%
(2) h (1+28%) = 44.8
h = 44.8 /(1+0.28) = 35 cm
(3) (1-35%) d = 1.82
d = 1.82 / (1-0.35)
d = 2.8m
(4) 交通費佔該月開支的百分比
= 1800 / (1800 +2500 +1700) *100% = 30%
(5) 30 (1-r%) = 20 (1+r%)
30r% + 20r% = 30 - 20
50r% = 10
r = (10/50 ) 100
= 20
1+r% = 26/20 = 1.3
r/100 = 0.3
r =30
(1b) 30 ( 1-r%) = 28.2
1-r% = 0.94
r/100 = 0.06
r = 6%
(2) h (1+28%) = 44.8
h = 44.8 /(1+0.28) = 35 cm
(3) (1-35%) d = 1.82
d = 1.82 / (1-0.35)
d = 2.8m
(4) 交通費佔該月開支的百分比
= 1800 / (1800 +2500 +1700) *100% = 30%
(5) 30 (1-r%) = 20 (1+r%)
30r% + 20r% = 30 - 20
50r% = 10
r = (10/50 ) 100
= 20
參考: me
2007-09-05 8:17 am
好心你自己做啦, 咁簡單既數.......
收錄日期: 2021-04-13 13:19:14
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https://hk.answers.yahoo.com/question/index?qid=20070904000051KK04885