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1.The size of a farm was decreased by 20%.The farmer then used new fertilizers and better seeds so that the yield per unit area was increased by 30%.What was the percentage change in the total yield of the farm?
初中數學 - Percentage Changes
2007-02-07 3:40 am
回答 (3)
2007-02-07 4:02 am
✔ 最佳答案
% change= [ (1 - 20%) (1 + 30%) - 1 ] x 100%
= ( 0.8 x 1.3 - 1 ) x 100%
= (1.04 - 1) x 100%
= +4%.
(+ means increase.)
2007-02-07 9:01 pm
Let 1 be the farm,
1x(1-20%)x(1+30%)
=0.8x130%
=1.04
so,the farm has increased 4%
:)
1x(1-20%)x(1+30%)
=0.8x130%
=1.04
so,the farm has increased 4%
:)
2007-02-07 4:07 am
let the original size of farm is x square units
the new size of farm is x*(1-20%)=0.8x square units
the yield in original farm is:
x*(1+30%)
=1.3x
the yield in new farm is:
0.8x*(1+30%)
=1.04x
the percentage change in the total yield of the farm:
1.04x - 1.3x /1.3x *100%
=-20%
thus, the percentage change in the total yield of the farm was decreased 20%
the new size of farm is x*(1-20%)=0.8x square units
the yield in original farm is:
x*(1+30%)
=1.3x
the yield in new farm is:
0.8x*(1+30%)
=1.04x
the percentage change in the total yield of the farm:
1.04x - 1.3x /1.3x *100%
=-20%
thus, the percentage change in the total yield of the farm was decreased 20%
收錄日期: 2021-04-12 23:28:54
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070206000051KK03051