全部都要用方程答,要列出所有steps
1)72 marbles are divided into two groups.7 times the number of marbles in the smaller group is equal to 5 times that in the larger group.Find the number of marbles in the smaller group.
2)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.
3)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 tickets is $86000,how many 4400 tickets are sold?
4)Bobby buys x pieces of fruit tarts and eats 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)The total price of 24 books is $405.Some of them are sold at $15 each and the others at $20 each.Find the number of books that are sold at $15 each.
6)Tork has $72.Sally has $12.In order to let Sally have 3 times the amount of York, how much should York give Sally?
7)A sum of money is planned to be evenly shared among 10 persons.Due to the absence of2 persons, each person present can get $30 more.Find the sum of money.
8)Carl has $9 more than David does.Hilbert has 1/3 of the amount of Carl.If they have a total amount of boys and girls there.
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.
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F.1數學問題~~急急急!請幫幫手!20點!
2009-11-23 2:32 am
回答 (2)
2009-11-23 3:07 am
✔ 最佳答案
1.Let x be the number of marbles in the smaller group,
then (72-x) is that in the larger group.
7x = 5(72-x) ..... (7 times small gp = 5 times large gp)
7x = 360 - 5x
12x = 360
x = 30
There are 30 marbles in the smaller group.
2.
Let x be the current age of Hebrew's son,
then (51-x) is that of Hebrew.
8(x-3) = 51-x-3 ..... (8 times son (3 yrs ago) = Hebrew (3 yrs ago))
8x - 24 = 48 - x
9x = 72
x = 8
Hebrew's son is now 8 years old.
3.
Let x be the number of $400-tickets sold,
then 4x is that of $200-tickets sold and 4x+380 is that of $100-tickets sold.
400x + 200(4x) + 100(4x + 380) = 86000
400x + 800x + 400x + 38000 = 86000
1600x = 48000
x = 30
30 $400-tickets are sold.
4.
x - x/4 - 7 = 2 ...... (original - Bobby - brothers&sisters = 2)
x - 0.25x = 9
0.75x = 9
x = 12
5.
Let x be the number of books that are sold at $15 each,
then (24 - x) is the number of books that are sold at $20 each.
15x + 20(24 - x) = 405
15x - 20x + 480 = 405
-5x = -75
x = 15
15 books are sold at $15 each.
6.
Let $x be the money that York should give Sally.
3(72 - x) = 12 + x
216 - 3x = 12 + x
204 = 4x
x = 51
York should give Sally $51.
7.
Let $x be the money that each people can get originally.
10x = (10-2) (x+30)
10x = 8(x+30)
10x = 8x + 240
2x = 240
x = 120
The sum of money = 120*10 = $1200.
8. What is the question?
9.
Let x be the number of girls in the class,
then (42 - x) is the number of boys in the class.
4x/3 = 42 - x
x = (3/4)(42 - x)
x = 31.5 - 3x/4
x + 3x/4 = 31.5
x + 0.75x = 31.5
1.75x = 31.5
x = 18
There are 18 girls and 18(4/3) = 24 boys in the class.
2009-11-22 20:40:10 補充：
10.
3x+2 + 4x-1 + x+20 = 69
8x + 21 = 69
8x = 48
x = 6
15.
I think the meaning of the question is that X and Y are points on AB,
then,
AX + XY + YB = AB
2x + 3x-2 + x+5 = 27
6x + 3 = 27
6x = 24
x = 4
Since AX = 2x, so AX = 2*4 = 8cm
2009-11-22 22:33:54 補充：
8.
Let $x be the money that Hilbert has,
then $(3x) is the money Carl has and $(3x-9) is the money David has.
x + 3x + 3x-9 = 61
7x - 9 = 61
7x = 70
x = 10
Hilbert has $10,
Carl has 3*10 = $30,
David has 30 - 9 = $21.
參考: ME, me, me
2009-11-23 2:52 am
1)Let m be the number of marbles in the smaller group
7m=5(72-m)
7m=360-5m
12m=360
m=30
Therefore,there hace 30 marbles in the smaller group
2)Let x be the current age of Hebrew's age
8(x-3)=51-p-3
8x-24=51-9-3
9p=75-3
p=8
Therefore,Hebrew's son is 8 years old
7)Let $x be the sum of money
x/10+30=x/8
8x-10x=-2400
x=1200
Therefore,The sum of money is $1200
7m=5(72-m)
7m=360-5m
12m=360
m=30
Therefore,there hace 30 marbles in the smaller group
2)Let x be the current age of Hebrew's age
8(x-3)=51-p-3
8x-24=51-9-3
9p=75-3
p=8
Therefore,Hebrew's son is 8 years old
7)Let $x be the sum of money
x/10+30=x/8
8x-10x=-2400
x=1200
Therefore,The sum of money is $1200
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