數學問題!!希望盡快回答!!

1 ) 809 , 2547 .3984 .2003 .213 .1997 的羅馬數字??

809 = DCCCIX
2547 = MMDXLVII
3984 = MMMCMLXXXIV
2003 = MMIII
213 = CCXIII
1997 = MCMXCVII


2) if the area of a rectangle is 40 cm^2 and its length and width are 8 cm and w cm respectively .find the value of w ?

8w = 40
w = 5


3) tom is 3 year younger than his sister .the sum of the ages of tom and his sister is 23 .how old is tom ?

Let y be the age of Tom = y
Then, the age of his sister = y + 3

y + (y + 3) = 23
2y + 3 = 23
2y = 20
y + 10

The age of Tom = 10


4) in a test ,mary get x marks and john gets 90 marks ,john's score is 10 less than twice mary 's ,find x ?

2x - 90 = 10
2x = 100
x = 50


5) 百份數化小數: 15又4 分之3

15又(3/4)%
= 15.75 x (1/100)
= 0.1575


6)小數化百份數: a)0.47 b )0.6 c) 0.016 d ) 3.048 e ) 1.015
a)
0.47
0.47 x 100%
= 47%

b)
0.6
= 0.6 x 100%
= 60%

c)
0.016
= 0.016 x 100%
= 1.6%

d)
3.048
= 3.048 x 100%
= 304.8%

e)
1.015
= 1.015 x 100%
= 101.5%

2. 40=(8+w)x2
w=12cm
3.let tom is x years old
x+x+3=23
x=20
tom is 20 years old