Peter claims that when a number x is increased by 10% and then decreased by 10%, the value of x is unchanged.
His calculation: x(1 + 10% - 10%) = x
Peter os wrong. Point out the mistake.
一條難度十分高的英文百分數題
2007-07-27 12:22 am
回答 (5)
2007-07-27 12:31 am
✔ 最佳答案
The equation should be X (1+10%) (1-10%) = X
The question means increment by 10% is X (1+10%) <= New amount
Then the increased amount decrease by 10%, i.e. the new amount times (1-10%)
So, it should be X (110%) (90%) =X
Then, 99% X = X
X seems equal to "0"
2007-07-27 12:31 am
Peter's calculation is wrong. The right method is as follows:
new value of X = (1+10%) (1-10%) X
= (1.1) (0.9) X
= 0.99X
Therefore, new value of X should become less.
new value of X = (1+10%) (1-10%) X
= (1.1) (0.9) X
= 0.99X
Therefore, new value of X should become less.
參考: myself
2007-07-27 12:29 am
x is increased by 10% ------>(1+10%)x = 1.1x
then decreased by 10%----> (1-10%)* 1.1x
----->0.99x
then decreased by 10%----> (1-10%)* 1.1x
----->0.99x
2007-07-27 12:26 am
When a number x is increased by 10%, it becomes 1.1x
And then decreased by 10%, it becomes 0.99x
The value of x has been decreased by 1%
His mistake is that the formula should be
x (1+10%)(1-10%) instead of x(1 + 10% - 10%)
And then decreased by 10%, it becomes 0.99x
The value of x has been decreased by 1%
His mistake is that the formula should be
x (1+10%)(1-10%) instead of x(1 + 10% - 10%)
2007-07-27 12:26 am
100% + 10% = 110%
110% * 0.9 = 99%
X went down from 100% to 99%
110% * 0.9 = 99%
X went down from 100% to 99%
收錄日期: 2021-04-23 19:43:25
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070726000051KK03115