F.1 Maths- -(全eng) (又有問題- -)

dead

  在下的代數不太好了- -
19題中有12題(?)不懂想請教大家
開始
1.After 16 years, Kenneth will be 2 times as old as he was 12 years old. Set up an equation for finding his current age.
2.In the figure,the perimeter of∆ABC is 91 cm. Find a.

                               
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3.In the Figure, if the perimeter of rectangle ABCD and square PQRS are the same,find the value ofx.

                               
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4.Bobby buys x pieces of fruit tarts and eat 1/4 of them.His brothers and sisters eat 7 pieces in total and there are 2 pieces left. Find the value of x.

5.In the figure,the length of AB is 27 cm. Find the length of AX
     2x cm             (3x-2) cm            (x+5) cm
|----------------|--------------------|--------------------|
A                   X                         Y                         B

6.The total price of 24 books is $405. Some of them are sold at $15 and others at $20. Find the number of books that sold at $15
each.

7.York has $72. Sally has $12. In order to let sally have 3 times the amount of York,how much should York give to Sally?

8.A sum of money is planned to be evenly shared among 10 persons. Due to the absence of 2 person, each person persent can get $30 more. Find the sum of money.

9. There are 42 students in S1A. The number of boys is 4/3 times of girls. Find the respective number of boys and girls there.

10.72 marbles are divided into two groups. 7 times the number of marbles in the smaller group in equal to 5 times that in the larger group. Find the number of marbles in the smaller group.

11.The total age of Hebrew and his son is 51. 3 years ago,Hebrew is 8 times as old as his son. Find the current age of Hebrew's son.

12.Concert tickets in $400, $200 and $100 each are available for sale. The number of $200 tickets sold is 4 times as many as that of $ 400 tickets. The number of $100 tickets sold is 380 more thanthat of $200 tickets. If the total income from the sale is $86000, how many $400 tickets are sold?

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請大家列出條數式和步驟,好讓我做功課時能知道如何做
謝謝大家了

Ｍaｙuｋi～＊

1) let x be his current age.
    16+x=2(12)
          x=8

2) 3a+(2a-1)+(4a+2)=91
            3a+2a+4a=91+1-2
                           a=9
3) (2x-6)(2)+(1/2x)(2)=7(4)
      4x-12+x=28
                 5x=40
                   x=8
5) 27-(3x-2)-(x+5)=2x
    27-3x+2-x-5=2x
    27+2-5=2x+3x+x
    24=6x
    4=x

先做咁多-__-
你諗多陣啦-_-...

dead

我盲係諗左好耐都諗唔到先上泥問- -
btw, 多謝你

Ｍaｙuｋi～＊

講真有d係睇唔明Q先set唔到equation

dead

因為我係英文痴(?)
所以睇唔明d q
同時自己都唔知點列式

dead

6# tamsunny

嘩! D ans好多呀
多謝哂呀
補完希望

Sunny

由於答案太亂，
重發

4.Bobby buys x pieces of fruit tarts and eat 1/4 of them.His brothers and sisters eat 7 pieces in total and there are 2 pieces left. Find the value of x.
x-1/4x-7 = 2
x-1/4x = 9
(4x-x)/4 = 9
3x = 36
  x = 12

6.The total price of 24 books is $405. Some of them are sold at $15 and others at $20. Find the number of books that sold at $15
each.
Let x and y be the number of books which sold at $15 and $20
  x + y = 24 -------------(1)
15x + 20y = 405 ---------(2)
From (2),
y = (405 - 15x)/20---------(3)
Sub (3) into (1),
x + (405-15x)/20 = 24
(405-15x)/20 = 24 – x
405-15x = 480-20x
5x = 75
x = 15
∴ the number of books that sold at $15 are 15.

7.York has $72. Sally has $12. In order to let sally have 3 times the amount of York,how much should York give to Sally?
Let $x be the amount that York should give to Sally.
Let $y be the amount of York after give x to Sally.
72-x = y----------- (1)
12+x = 3y----------(2)
Sub (1) into (2),
12+x = 3(72-x)
12+x = 216-3x
4x = 204
x = 51
∴ York should give $51 to Sally.

8.A sum of money is planned to be evenly shared among 10 persons. Due to the absence of 2 person, each person persent can get $30 more. Find the sum of money.
Let the sum of money be x.
x/10+30 = x/8
(x+300)/10 = x/8
8x+2400 = 10x
2x = 2400
x = 1200
∴the sum of money is $1200.
9. There are 42 students in S1A. The number of boys is 4/3 times of girls. Find the respective number of boys and girls there.
Let the number of girls and boys be x and 4/3x
x + 4/3x = 42
(3x+4x)3 = 42
7x = 126
x = 18

4/3x
= 4/3(18)
= 72/3
= 24
∴The number of girls are 18.
  The number of buys are 24.

10.72 marbles are divided into two groups. 7 times the number of marbles in the smaller group in equal to 5 times that in the larger group. Find the number of marbles in the smaller group.
Let x and y be the number of marbles in the the smaller group and large group.
x + y = 72---------- (1)
7x = 5y----------- (2)
From (1),
x = 72-y----------- (3)
Sub (3) into (2),
7(72-y) = 5y
504-7y = 5y
12y = 504
y = 42----------- (4)
Sub (4) into (1),
x + 42 = 72
x = 30
∴ the number of marbles in the the smaller group and large group are 30 and 42.

11.The total age of Hebrew and his son is 51. 3 years ago,Hebrew is 8 times as old as his son. Find the current age of Hebrew's son.
Let x and y be the age of Hebrew and his son.
x + y = 51----------- (1)
x-3 = 8(y-3)----------- (2)
From (1),
x = 51-y----------- (3)
Sub (3) into (2)
51-y-3 = 8(y-3)
48-y = 8y-24
9y = 72
y = 8----------- (4)
Sub (4) into (1)
x+8 = 51
x = 43
∴ the age of Hebrew is 43.
the age of his son is 8.

12.Concert tickets in $400, $200 and $100 each are available for sale. The number of $200 tickets sold is 4 times as many as that of $ 400 tickets. The number of $100 tickets sold is 380 more than that of $200 tickets. If the total income from the sale is $86000, how many $400 tickets are sold?
Let x ,y and z be the number of $400, $200 and $100 tickets are sold.
y = 4x----------- (1)
z = y+380----------- (2)
400x+200y+100z = 86000----------- (3)
From (1),
y = 4x
y/4 = x ----------- (4)
Sub (2) and (4) into (3)
400(y/4)+200y+ 100(y+380) = 86000
100y + 200y +100y + 38000 = 86000
400y = 48000
   y = 120----------- (5)
Sub (5) into (1),
120 = 4x
  x = 30

∴The number of $400 tickets sold is 30.

dead

7# tamsunny
冇所謂啦
我睇得明架
唔洗重發wo

dead

今日老師改左10-12題
佢話d q要用only one unknow
請大家指教orz

rose~

由於答案太亂，
重發

4.Bobby buys x pieces of fruit tarts and eat 1/4 of them.His brothers and sisters eat 7 pieces in total and there are 2 pieces left. Find the value of x.
x-1/4x-7 = 2
x-1/4x  ...
tamsunny 發表於 21/11/2009 06:39 PM

                               
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我覺得elimination較好用- -

----------------------(更可愛的分格線)----------------------
10. 72 marbles are divided into two groups. 7 times the number of marbles in the smaller group in equal to 5 times that in the larger group. Find the number of marbles in the smaller group.

Let x be the number of marbles in the larger group,
Then (72-x) is the number of marbles in the smaller group

7(72-x)=5x
504-7x=5x
504=12x
x=42

(72-42) is the number of marbles in the smaller group

∴ There 30 marbles in the smaller group.

11.The total age of Hebrew and his son is 51. 3 years ago,Hebrew is 8 times as old as his son. Find the current age of Hebrew's son.

Let x be the age of Hebrew now,
then (51-x) is the age of his son.

x-3=8(51-x-3)
x-3=384-8x
9x=387
x=43

(51-43) is the age of his son now.

∴ His son is now 8 years old.

12.Concert tickets in $400, $200 and $100 each are available for sale. The number of $200 tickets sold is 4 times as many as that of $ 400 tickets. The number of $100 tickets sold is 380 more than that of $200 tickets. If the total income from the sale is $86000, how many $400 tickets are sold?

Let x be the number of $400 ticket sold,
Then 4x is the number of $200 ticket sold,
(4x+380) is the number of $100 ticket sold.

400x+200(4x)+100(4x+380)=86000
400x+800x+400x+38000=86000
1600x=48000
x=30

∴30 $400 ticket are sold.