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1. The difference between two numbers is 24 .If twice the smaller number is subtracted form 3/4 of the greater number, the diffence is 3 .Find the greater number .
2. David spends 45 mins on mathematics homework and this makes up 20 % of his total time spent on school homework .How many hours does David spend on school homework?
3. For the year 2003, 11% of the labour force in Hong Kong were aged under 25 *.If the number of people in the labour force,aged 25 or above , was 3 105 000 ,find the total number of people in the labour force in that year.
F.1的數黎的!!!
Maths 3 條!!!急!!要今日之內答! 20點..
2008-11-13 3:04 am
回答 (3)
2008-11-13 4:17 am
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2008-11-13 3:34 am
1. Let X be the smaller number and Y be the greater number
X = Y - 24 ----> A
3/4 Y = 2X + 3 ----> B
Sub A into B
3/4 Y = 2(Y-24) + 3
3/4 Y = 2Y-48+3
5/4 Y = 45
Y = 36
The greater number is 36.
2. Let Y be the total hours David spends on school homework
Y x 20% = 3/4
Y = 3/4 * 5
Y = 3 3/4
David spends 3 3/4 hours (3 hours and 45 mins) on school homework.
3. Let Y be the total number of people in the labour force in 2003.
Y x (1-11%) = 3,105,000
Y = 3,105,000 / 89%
Y = 3,488,764
The total number of people in the labour face in 2003 is 3,488,764.
2008-11-14 01:45:26 補充：
補充第三題：
The total number of people in the labour face in 2003 is 3,490,000.
(因取至萬位)
X = Y - 24 ----> A
3/4 Y = 2X + 3 ----> B
Sub A into B
3/4 Y = 2(Y-24) + 3
3/4 Y = 2Y-48+3
5/4 Y = 45
Y = 36
The greater number is 36.
2. Let Y be the total hours David spends on school homework
Y x 20% = 3/4
Y = 3/4 * 5
Y = 3 3/4
David spends 3 3/4 hours (3 hours and 45 mins) on school homework.
3. Let Y be the total number of people in the labour force in 2003.
Y x (1-11%) = 3,105,000
Y = 3,105,000 / 89%
Y = 3,488,764
The total number of people in the labour face in 2003 is 3,488,764.
2008-11-14 01:45:26 補充：
補充第三題：
The total number of people in the labour face in 2003 is 3,490,000.
(因取至萬位)
參考: 自己
2008-11-13 3:26 am
1. Let A and B be the greater and smaller numbers respectively.
Given A-B=24, therefore B=A-24
Given 3/4(A)-2B=3
3A-8B=12
3A-8(A-24)=12
3A-8A+192=12
5A=192-12
5A=180
A=36
The greater number is 36.
2. Let A be the number of hours David spends on school homework.
20% A = 45 min.
20% A = 0.75 hour
A = 3.75 hours
David spends 3 hours and 45 min on school homework.
3. The total number of people in the labour force
= 3 105 000 / (1-11%)
= 3 488 764 (rounded)
Given A-B=24, therefore B=A-24
Given 3/4(A)-2B=3
3A-8B=12
3A-8(A-24)=12
3A-8A+192=12
5A=192-12
5A=180
A=36
The greater number is 36.
2. Let A be the number of hours David spends on school homework.
20% A = 45 min.
20% A = 0.75 hour
A = 3.75 hours
David spends 3 hours and 45 min on school homework.
3. The total number of people in the labour force
= 3 105 000 / (1-11%)
= 3 488 764 (rounded)
收錄日期: 2021-04-13 16:13:58
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