中學既數學問題..急要..[15點] @ wszspj2的部落格

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中學既數學問題..急要..[15點]

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1. n+0.1/0.3 - n-0.1/0.2 = n+1.2/0.8 n=?2. In a club, 1/3 of the members are male.This becomes 2/5 when 4 new male members join the club.Find the new number of members in the club.3. Tom has some $1,$2 and $5 coins.It is known that the number of $1 coins is 2 times the number of $5 coins,while the number of... 顯示更多 1. n+0.1/0.3 - n-0.1/0.2 = n+1.2/0.8 n=? 2. In a club, 1/3 of the members are male.This becomes 2/5 when 4 new male members join the club.Find the new number of members in the club. 3. Tom has some $1,$2 and $5 coins.It is known that the number of $1 coins is 2 times the number of $5 coins,while the number of $2 coins is less than that of $1 coins by 7.If the total value of the coins is $85,find the number of $2 coins. 4. Tom made a profit of $432today by selling newspapers and magazines. The total number of newspapers and magazines sold was 136.If the profits of selling each newspapers and each magazines were $2.4 and $4.6,which type of publication sold today contributed a greater profit? 5. Mary has 2 bags of marbles.The total number of marbles is 162.She draws 1/4 of the marbles from bag A and puts them into bag B.The number of marbles in bag A is then 30 more than that in bag B.Find the original number of marbles in each bag. 要題解..仲有全部題目都要有計算過程..唔該哂大家啦!! 小妹我急要=v=

最佳解答:

Question 1. n+0.1/0.3 - n-0.1/0.2 = n+1.2/0.8 n=? n +1/3 –n – 1/2 = n + 3/2 1/3 - 1/2 -3/2 = n n = - 1 2/3 or – 1.6667 (4 decimal place) Question 2. Let x be new number of members in the club. (x – 4) = original number of member in the club New Number of males 1/3 (x - 4) + 4 = 2/5 (x) 1/3 (x) -4/3 + 4 = 2/5 (x) Multiply by 5 to get rid of fraction 5x -20 + 60 = 6x -20 + 60 = 6x – 5x 40 = x x = 40 The new number of members in the club = 40. Question 3. Let x be the number of $2 coins. The number of $1 coins = x + 7 The number of $5 coins = ? (x + 7) The total value = $1(x +7) + $2(x) + $5[1/2(x + 7)] $85 = $1(x +7) + $2(x) + $5[0.5x + 3.5] 85 = x +7 + 2x + 2.5x + 17.5 85 = 5.5x + 24.5 5.5x = 85 - 24.5 5.5x = 60.5 x = 11 the number of $2 coins = 11 Question 4. Let the number of newspapers sold = x Let the number of magazines sold = 136 – x Profit by selling newspapers = $2.40 (x) Profit by selling magazines = $4.60 (136 - x) Total profit = Profit from newspapers + Profit from magazines $432 = $2.40 (x) + $4.60 (136 - x) 432 = 2.4x + 4.6 (136) – 4.6x 432 = 2.4x + 4.6 (136) – 4.6x 432 = 2.4x + 625.6 – 4.6x 4.6 x – 2.4x = 625.6 - 432 2.2x = 193.6 x = 88 Number of newspapers sold = 88 Number of magazines sold = 136 – 88 = 48 Profit from newspapers = $2.40 (88) = $211.20 Profit from magazines = $4.60 (48) = $220.80 Magazines sold today contributed a greater profit ($220.80 > $211.20) Question 5. Let x be the original number of marbles in bag A Let (162 – x) be the original number of marbles in bag B The new number of marbles in bag A = ? x The new number of marbles in bag b = (162 – x) + 1/4x ? x – [(162 – x) + 1/4x] = 30 ? x – [162 – 3/4x] = 30 ? x – 162 + 3/4x = 30 ? x + 3/4x = 30 + 162 1.5 x = 192 x = 192/1.5 = 128 Original number of marbles in bag A is 128 Original number of marbles in bag B is (162 – 128) = 34

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