幾條數學文字題,,急！！最好有埋式!!THX!!

2) Let X be the amount of money that Mr. Chan originally has.
　1st day, he spent 30% = 0.3X
　2nd day, he spent 25% of the remaining amount
　　= X(1-0.3) x 25% = 0.175X
　Money left = X - 0.3X - 0.175X = $1680
　　　　　　　　　　　　　X = 3200
　(a) Mr. Chan originally has $3200
　(b) If Mr. Chan spent another $320,
　　total he has spent = 0.3X + 0.175X + 320= 1840
　　percentage of total spent = 1840/3200 = 57.5%
3) numderator : 3
　increased by 20% = 3.6
　denominator : 5
　decreased by 10% = 4.5
　(a) new fraction = 3.6 / 4.5 = 4/5
　(b) precentage changed:
　　　(4/5 - 3/5) / (3/5) = (1/5) / (3/5)
　　　　　　　　　　　 = 1/3 or 33.33%
　　 The new value is increased by 33.33%.

2a) let X be the sum of the money
Day 1 spent : X x 30%= 0.3X
Day 2 spent : X x 70% x 25% = 0.175X

X - 0.3X - 0.175X =1680
0.525X = 1680
X = 3200
He orginal had $ 3200.

2b) Day 1 spent $3200 x 30% = $960
Day 2 apent $ 3200 x 70% x 25% = $ 560
All together spent : $960+$ 560 + $320 = $1840
% = ($1840/$3200) x 100%
= 57.5% //

3a) 3 (1+20%)
---------------------------
..... 5 (1-10%)

= 3 / 5 x 4 / 3

= 4 / 5 //

3b) 4 / 5 - 3 / 5
---------------------- x 100%
............ 3/ 5

= 1/ 3 x 100%

= 33. 33 %(to 2 dec)//


(不用理會 那些 "..........." , 因不能留打入空位)


加油!!

2a)The original $ on the second day
= $1680/ (1 - 0.25)
= $1680/ 0.75
= $2240

SO, the $ he have originally ,
= $2240 / (1 - 0.3)
= $2240/ 0.7
= $3200

2b) He had spent altogether

= $3200 * 0.3 + $2240 * 0.25 + $320
= $ 960 + $ 560 + $320
= $1840

So, the percentage of the money did he spend altogether

= ( $1840 / $3200 ) * 100%
= 57.5%

2006-12-03 16:22:29 補充：
3a)Find the new fraction.New numderator=3 * 1.2=3.6New denominator= 5 * 0.9=4.5New fraction.= 3.6/4.5= 0.8=4------5

2006-12-03 16:23:51 補充：
3b)Find the precentage increase or decrease in value. Orignal= 3/5New = 4/5So, New Orignal=4/5 - 3/5---------------X 100%3/5= 33.33% (correct to 2 sig.fig)=========================如果不選我，請盡快通知我刪除~ thanks!^^