Question 691413
The sum of the digits of a two digit number is 10. The number formed by reversing the number is 4 less than 5 times the number. Find the original number? 
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Let the number be 10t+u ; t is the 10's digit; u is units digit
The reverse number is 10u + 5
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Equations:
t + u = 10
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10u+t = 5(10t+u)-4
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Simplify the bottom equation:
10u+t = 50t+5u-4
49t - 5u = 4
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Substitute for t = 10-u for "t" and solve for "u":
49(10-u) - 5u = 4
490 - 54u = 4
54u = 486
u = 9
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Now, solve for "t" using t + u = 10
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t+9 = 10
t = 1
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The number is 10t+u = 10*1 + 9 = 19
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Cheers,
Stan H.
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