Math Problem?
2016-07-17 2:19 pm
What number, when added to the numerator and to the denominator of 5/8, results in a fraction whose value is 0.4?
回答 (7)
2016-07-17 2:26 pm
Let n be the number.
(5 + n) / (8 + n) = 0.4
5 + n = 0.4 × (8 + n)
5 + n = 3.2 + 0.4n
n - 0.4n = 3.2 - 5
0.6n = -1.8
n = -3
The number = -3
(5 + n) / (8 + n) = 0.4
5 + n = 0.4 × (8 + n)
5 + n = 3.2 + 0.4n
n - 0.4n = 3.2 - 5
0.6n = -1.8
n = -3
The number = -3
2016-07-18 7:41 am
x = -3
2016-07-17 8:19 pm
[ 5 + x ] / [ 8 + x ] = 0.4
5 + x = 3.2 + 0.4x
0.6 x = - 1.8
6x = - 18
x = - 3
5 + x = 3.2 + 0.4x
0.6 x = - 1.8
6x = - 18
x = - 3
2016-07-17 5:43 pm
-3
2016-07-17 2:40 pm
Let x be the number
5/8 = (x+5)/(x+8) =0.4
(x+5)/(x+8) = 4/10
cross multiply
10(x+5) = 4(x+8)
10x+50 = 4x+32
6x = -18
x=-3
5/8 = (x+5)/(x+8) =0.4
(x+5)/(x+8) = 4/10
cross multiply
10(x+5) = 4(x+8)
10x+50 = 4x+32
6x = -18
x=-3
2016-07-17 2:36 pm
(5+x)/(8+x) = 0.4
(5+x) = (2/5)(8+x)
5(5+x) = 2(8+x)
25 + 5x = 16 + 2x
3x = -9
x = -3.
(5+x) = (2/5)(8+x)
5(5+x) = 2(8+x)
25 + 5x = 16 + 2x
3x = -9
x = -3.
2016-07-17 2:29 pm
(5+x)/((8+x) = 4/10 = 2/5
5(5+x) = 2(8+x)
25+5x = 16+2x
3x = -9
x = -3
check
(5-3)/(8-3) = 2/5
you might be tempted to do
5+x = 2 -> x = -3
8+x = 5 -> x = -3
x = -3
But actually
5+x = 2k
8+x = 5k
x = 2k-5 = 5k-8
3k = 3
k = 1
x = -3
5(5+x) = 2(8+x)
25+5x = 16+2x
3x = -9
x = -3
check
(5-3)/(8-3) = 2/5
you might be tempted to do
5+x = 2 -> x = -3
8+x = 5 -> x = -3
x = -3
But actually
5+x = 2k
8+x = 5k
x = 2k-5 = 5k-8
3k = 3
k = 1
x = -3
收錄日期: 2021-04-18 15:20:22
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20160717061919AAp5HE9