mathematics

吸血鬼

2010-11-26 3:45 am

The sum of the hundreds didit and the ten digit of a three digit number is 13.If the hundreds digit and the ten digit are interchanged, the new number is 90 less than the original number. It is given that the units digit of the original number is 4.Find the original number.(show step)

Thankyou

回答 (1)

[匿名]

2010-11-26 3:50 am

✔ 最佳答案

let x be the hundreds didit and y be the ten digit
{x+y=13
{100x+10(4)+y=[100y+10(4)+y]-90

2010-11-25 19:50:43 補充：
{x+y=13 ------(1)
{100x+10(4)+y=[100y+10(4)+y]-90 ------(2)
From(1), x=13-y,

2010-11-25 20:10:20 補充：
sorry , the answer should be this- -
{x+y=13 ----------------(1)
{100y+10x+4=(100x+10y+4)-90 --------------(2)
from (1) , x=13-y --------(3)
100y+10(13-y )+4=[100(13-y)+10y+4]-90
180y=1080
y=6
sub. y=6 into (3)
x=13-6
x=7
.'. the original number is 764 ,,

參考: me

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