中二maths.入黎解答下啦:)

[匿名]

2011-09-17 3:10 am

1. x:y=y:z=3:5

2. Amy, Alice and Angela share a bar of 550 g chocolate. The ratio of Amy's share to Alice's share is 2 : 1. The ratio of Amy's share to Angela's share is 3 : 1. How many grams of chocolate does each of them get?

3. 140 stamps are to be shared by Ada, Billy and Candy. Ada gets twice as many as Billy, and the number of stamps Candy has is 1/6 that of Ada.
(a) Find Ada's share : Billy share : Candy's share.
(b) How many stamps does each on get?

4. A sum of money is shared by two persons A and B in the ratio 7 : 5. If B obtains $40 less than A, what is the sum of money?

5. A packet of candies is to be shared by Amy, Harry and Jill in the ratio 2 : 4 : 3. If Amy gets 10 candies,
(a) how many candies are there in total?
(b) how many candies do Harry and Jill get respectively?

6.The wight of a tortoise is half that of a cat, and the weight of the cat is 1/4 that of a dog.
(a) Find the weight of the tortoise : the weight of the cat : the weight of the dog.
(b) If the dog weighs 20 kg, find
(i) the weight of the tortoise,
(ii) the total weight of the three pets.

7. Angie and Leslie have 48 and 72 story books respectively. If Angie borrows some story books from Leslie, the ratio of the number of Angie's books to that of Leslie becomes 13 : 17. Find the number of books that Angie borrowed from Leslie.

更新1:

唔該啦..我真係唔識做..

更新2:

唔該啦...冇人識?

回答 (1)

ShikaP

2011-09-17 5:42 am

✔ 最佳答案

1.you mean...
x:y:z
=3*3:3*5:5*5
=9:15:25

2. iq Alices's : amy's=1:2
then
Alices's : amy's : angela's
=1*3:2*3:2*1
=3:6:2
Alices get 550*(3)/(3+6+2)=150g chocolate
Amy get 550*6/11=300g chocolate
Angela get 100g (=550-300-150) chocolate
3.a)let
A(da)=2B(liy)
C(andy)=A(da)/6
iq 6C=A
A:B=2:1
C:A=1:6
iq. C:A:B=1*2:2*6:6*1
=2:12:6
=1:6:3
iq. A:B:C=6:3:1

b)
Ada get 140*(6)/10=84 stamps
Billy get 140*3/10=42 stamps
Candy get 140/10=14 stamps

4.
A:B=7:5,then iq. 5a=7b
B+40=A...(2)

take (1) into (2),5(b+40)=7b
5b+200=7b

b=100
a=7/5*100=500/7
a+b=100+500/7=171.43...=171,cor to 4 sig fig

5.let there are x candies,
amy get 10 candies
=x*2/(2+4+3)
=2x/9
10=2x/9
x=45
there are 45 candies
b) Harry=45*4/9=20 candies
Jill = 45*3/9=15 candies

6.let
tortoise:cat=a:b=1/2
cat:dog=b:c=1/4
then a:b:c
=1*1:2*1:2*4
=1:2:8
so the weight of the tortoise : the weight of the cat : the weight of the dog.
is 1:2:8
b)i
let the total weight of the three pets is xkg
then the dog's weight is
=20
=x*8/(1+2+8)
=8x/11
20=8x/11
x=27.5
tortoise's weight
=27.5*1/11
=2.5v kg
b)ii
from b)i,the total weight of the three pets is 27.5kg

7.when Angie borrows x story books from leslie,
the ratio of the number of Angie's books to that of Leslie becomes
13:17=48+x:72-x
936-13x=816+17x
120=30x
x=4
Angie borrowed 4 books from Leslie

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