#1 The sum of two digits of two-digit number is 13. If the digits are reversed, the number will be decreased by 9. Find the original number.
如何列方程?thz.
S.2 MTH linear equation ..急!!!
2011-12-23 5:53 am
回答 (1)
2011-12-23 6:05 am
✔ 最佳答案
Let 10x + y be the number , thenx + y = 13 ..........(1)If the digits are reversed , the number is 10y + x , so
(10x + y) - (10y + x) = 9
9x - 9y = 9
x - y = 1 .........(2)
(1) + (2) :2x = 13 + 1
x = 7 , then
y = 6
The original number is 76.
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