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Question 763388: a two digit number is 4 more than six times the sum of its digits. if 18 is subtracted from the number,the digits are reversed.find the number.
Answer by nerdybill(7384)   (Show Source):
You can put this solution on YOUR website! a two digit number is 4 more than six times the sum of its digits. if 18 is subtracted from the number,the digits are reversed.find the number.
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Let x = ones digit
and y = tens digit
then from "a two digit number is 4 more than six times the sum of its digits":
x + 10y = 6(x+y)+4
x + 10y = 6x+6y+4
10y = 5x+6y+4
4y = 5x+4
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and, from "if 18 is subtracted from the number,the digits are reversed.find the number"
x+10y -18 = y+10x
10y -18 = y+9x
9y -18 = 9x
y -2 = x
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substitute the above into:
4y = 5x+4
4y = 5(y-2)+4
4y = 5y-10+4
4y = 5y-6
4y+6 = 5y
6 = y
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substitute above into:
4y = 5x+4
4(6) = 5x+4
24 = 5x+4
20 = 5x
4 = x
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The number is 64
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