Maths 的問題 fast!!!!

2008-11-02 8:17 pm

1.If two paralle sides of a square are each increased by 8m and other two
paralle sides are each decreased by 2m,a rectangle with a perimeter of 40m is
formed.Find the length of a side of the square.

2.The length of a rectangle is 6m longer than three times the width.If the
perimeter is 76m,find:
(a)the width of the rectangle
(b)the area of the rectangle

3.A watch lost x minutes on monday,2x minutes on tuesday and 3x minutes on
wednesday.Altogether the total loss was 9 minutes.How many minutes did it
lose on tuesday?

4.In a class of 45 students,the number of girls is more than the number of boys
by 11.
(a)How many girls are there in class?
(b)How many boys are there in class?

5.The total coast of a handkerchief and a shirt is $112.The cost of the shirtis 3
times as much as that of the handkerchtef.
(a)Find the cost of the shirt.
(b)What is the difference in cost between the shirt and the handkerchief?

6.Steve is 24 years old.He is now twice as old as his yonger brother.n years
ago,Steve was three times as old as his yonger brother.Find the value of n.

7.Vivian is four years older than her sister.Eight years later,the sum of their
age will be 44.Find their present ages.

8.Anna's weight is 16 kg more than Betty's weight .Betty's weight is 4 kg
less than Kevin's weight . If their total weight is 134kg,find the weight of
each person.

(All question use Algebra)

回答 (1)

用戶22403

2008-11-03 6:28 am

✔ 最佳答案

1. let y is the length of the square
[(y+8)+(y-2)]x2=40
2y+6=40/2
2y=20-6
2y=14
y=7
the length of the square = 7m

2a. let y is the the width of the rectangle
[y+(3y+6)]x2=76
4y+6=76/2
4y=38-6
4y=32
y=8
the width of the rectangle is 8m
b. area of the rectangle
=y(3y+6)
=8(3x8+6)
=8(24+6)
=8x30
=240m^2

3. NOT SURE

4. let y is the numbers of boys. then y+11 is the numbers of girls
y+(y+11)=45
2y+11=45
2y=45-11
2y=34
y=17
a. the numbers of girls = y+11 = 17+11 =28
b. the numbers of boys = y = 17

5. let y is the cost of handkerchief, then 3y is the cost of the shirt
y+3y=112
4y=112
y=28
a. the cost of the shirt = 3y = 3(28) = 84
b. their difference = 3y - y = 2y = 2(28) = 56

6. age of Steve = 2 x age of his young brother
24=2 x age of his young brother
age of his young brother = 24/2 = 12
24-n = 3 x (12-n)
24-n = 36-3n
3n-n = 36-24
2n = 12
n = 6

7. let y is the age of Vivian's sister, then y+4 is the age of Vivian
(y+8)+(y+4+8)=44
2y+20=44
2y=44-20
2y=24
y=12
the age of Vivian = y+4 = 12+4 = 16
the age of her sister = y =12

8. let y is the weight of Kevin, then y-4 is the weight of Betty,
and y-4+16 is the weight of Anna.
y+(y-4)+(y-4+16)=134
3y-4-4+16=134
3y+8=134
3y=134-8
3y=126
y=42
the weight of Kevin = y = 42
the weight of Betty = y-4 = 42-4 = 38
the weight of Anna = y-4+16 = 42-4+16 = 54

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