1. How many km is it between two places ,if a car travelling 2d km an hour takes 3 hours to finish the journey ?
2. The length and width of a rectangle are 30 cm and 20 cm respectively . If the length is increased by 20% and the width is decreased by 20% ,find
(a) the new area of the rectangle
(b) the percentage increase ?decrease in the area of the rectangle.
3. The height of a boy is 150 cm .If the percentage error is 2% ,the maximum error is _______.
Maths
2008-08-07 10:25 pm
回答 (1)
2008-08-07 10:44 pm
✔ 最佳答案
1.the distance=2(3)=6km
2.
(a) new area of the rectangle
=30(1+20%)*20(1-20%)
=30(1.2)*20(0.8)
=576cm^2
(b)
the original =30*20=600cm^2
the percentage decrease
=(600-576)/600*100%
=4%
3/
the maximum error=150*2%=150*0.02=3cm
收錄日期: 2021-04-22 00:35:46
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