MATHS QUESTIONS Form2 急

2012-01-18 4:41 am

1. A box of stickers is shared among three children in the ratio 7:5:4.
If one child gets 3 stickers more than the other but 6 stickers less than the third child , find the total number of stickers .

2. If $5200 is shared among three people in the ratio 1/4 : 1/2 : 1/3 ,
find the amount received by the person with the smallest share .

3. In a secondary school , the ratio of the number of teachers to the numbers of students is 7:200 . The total number of teachers and students
is 1035 .
a) Find the number of teachers and the number of students .
b) In April , n students leave the school to sit for a public examination .
If the ratio of the number of teachers to the number of students changes
to 1:25 , find the value of n.

4. A sum of $165 is divided among A,B and C so that B gets twice as
much as A , and three times as much as C.
a) Find :
A's amount : B's amount
B's amount : C's amount
A's amount : B's amount : C's amount
b) Find the amount of each person receives .

Please give all steps and fast please !
Need to hand in tmr

回答 (1)

Godfrey

2012-01-18 2:57 pm

✔ 最佳答案

1:
Let n be the total number of stickers
5/(7+5+4) n – 4/(7+5+4) n = 3
5/16x – 4/16x = 3
(5-4)/16 n = 3
1/16 n = 3
n= 16 x 3 = 48
total number of stickers = 48

Check
child A gets 48 x 7/16 = 21 stickers (the most)
child B gets 48 x 5/16 = 15 stickers
child C gets 48 x 4/16 = 12 stickers (the least)
child B gets 3 stickers more than child C = 15 -12 = 3
child B gets 6 stickers less than child A = 21 – 15 = 6

2.
ratio 1/4 : 1/2 : 1/3 (multiplied by 12)
ratio :3 : 6: 4
The smallest share = $5200 x 3/(3+6+4) = $5200 x 3/13 = $1200
The smallest share = $1200

3. a) Find the number of teachers and the number of students .
Number of teachers = 1035 x 7/(7+200) = 35
Number of students = 1035 – 35 = 1000 (or 1035 x 200/207 = 1000)

b) In April, let n be the number of student who had left
Ratio of teacher to student – 1: 25
1/25 =35/(1000 – n)
1000 – n = 35 x 25
1000 – n = 875
n = 1000 – 875 = 125
n = 125

4.
a) Find :
A's amount : B's amount
B's amount : C's amount
A's amount : B's amount : C's amount
b) Find the amount of each person receives .

a)
Let B's amount be n
A get ½ n
C gets 1/3 n
Ratio : ½ n : n :1/3 n
Multiplied by 6
Ratio of A:B:C 3n : 6n: 2n, 3:6:2
Ratio of A's amount : B's amount 1:2
Ratio of B's amount : C's amount 3:1
Ratio of A’s amount: B's amount: C's amount 3:6:2

b) A gets $165 x3/(3+6+2) =$165 x3/11 = $45
B gets $165 x6/(3+6+2) =$165 x6/11 = $90
C gets $165 x2/(3+6+2) =$165 x2/11 = $30

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