1.when a number is added to both the number and denominator of the fration 6/13,its value is 3/5.find the number.(我唔知點例條方程式)
2.may has 54 coins which are either 20-cent coins or 50-cent coins.if the total amount is $20.7,how many 20-cent coins does may have?
f.1math
2008-01-01 5:43 am
回答 (2)
2008-01-01 9:07 pm
✔ 最佳答案
1. Denote x as the number(6+x)/(13+x)=3/5
5(6+x)=3(13+x)
30+5x=39+3x
x=9/2
2. Denote x as the numbers of 20-cent, y be the 50-cent
x+y=54
y=54-x-------------α
0.2x+0.5y=20.7-----------------β
Subsitute α into β
0.2x+0.5(54-x)=20.7
0.2x+27-0.5x=20.7
0.3x=6.3
x=21
∴There is 21 20-cent coins
參考: me
2008-01-01 5:47 am
let x be the number
1. 6+n/13+n=3/5
1. 6+n/13+n=3/5
收錄日期: 2021-04-13 18:01:07
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