Q1. The numerator and the denominator of a fraction are positive integers and their sum equals 11. If 5 is added to both integers, the resulting fraction becomes 1/2. Find the original fraction.
The answer is 2/9.
Q2. Candy was 3 times as old as her son 10 years ago. If she is now twice as old as her son, Find Candy's age now.
The answer is 40.
Please show steps. Thx. a lot.
中2數學 2題 (3)
2010-03-06 9:56 pm
回答 (2)
2010-03-06 10:02 pm
2010-03-07 2:15 am
A1. let numerator be x, denominator be y.
x+y=11 --> equation (1)
(x+5)/(y+5)=1/2 --> equation (2)
From (2),
2(x+5)=y+5
2x=y-5
x=(y-5)/2 --> equation (3)
Sub (3) into (1),
(y-5)/2+y=11
(y-5)+2y=22
3y=27
y=9
Put y=9 into (1),
x=2
A2. Let Candy's age be x, son's age be y
x-10=3(y-10) -->equation (1)
x=2y -->equation (2)
Put (2) into (1),
2y-10=3y-30
y=20
Put y=20 into (2),
x=40
x+y=11 --> equation (1)
(x+5)/(y+5)=1/2 --> equation (2)
From (2),
2(x+5)=y+5
2x=y-5
x=(y-5)/2 --> equation (3)
Sub (3) into (1),
(y-5)/2+y=11
(y-5)+2y=22
3y=27
y=9
Put y=9 into (1),
x=2
A2. Let Candy's age be x, son's age be y
x-10=3(y-10) -->equation (1)
x=2y -->equation (2)
Put (2) into (1),
2y-10=3y-30
y=20
Put y=20 into (2),
x=40
收錄日期: 2021-04-23 20:42:03
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100306000051KK00720