Use method of substitution or method of elimination to solve the simultaneous equation.
In a three-digit number, the sum of the hundreds digit and tens digit is 13. When these two digits are interchanged, the value of the number decreases by 90. If the units digits is 4, find the original number
F.2 maths Applications Of Simultaneous Linear Equation
2008-02-04 8:27 am
回答 (1)
2008-02-04 8:35 am
✔ 最佳答案
Let x be the hundreds digit and y be the tens digit.x + y = 13 ... (1)
(100x + 10y) - (100y + 10x) = 90 ... (2)
From (1), y = 13 - x ... (3)
Substitute (3) into (2),
90x - 90(13 - x) = 90
2x - 13 = 1
x = 7
Substitute x=7 into (3),
y = 13 - 7 = 6
Hence, the original number is 764.
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