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Question 1133719: In a two digit number, the unit digit is 3 greater than the ten's digit. Find the number. If it is 4 times a large as the sum of it digit.
Found 3 solutions by josgarithmetic, Alan3354, greenestamps:
Answer by josgarithmetic(39620)   (Show Source):
Answer by Alan3354(69443)  (Show Source):
You can put this solution on YOUR website! In a two digit number, the unit digit is 3 greater than the ten's digit. Find the number. If it is 4 times a large as the sum of it digit.
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T = U-3
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If it is 4 times a large as the sum of it digit. [sic] its digits.
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10T + U = 4*(T+U)
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Sub for T
10(U-3) + U = 4*(U-3 + U)
11U - 30 = 8U - 12
3U = 18
U = 6
T = 3
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Number is 36
Answer by greenestamps(13203)  (Show Source):
You can put this solution on YOUR website!
Solving the problem using formal algebra is a good exercise....
But if an algebraic solution is not required, solving the problem by logical reasoning is also good brain exercise... and gets you to the answer MUCH faster.
The units digit is 3 more than the tens digit. That means the possible 2-digit numbers are 14, 25, 36, 47, 58, and 69.
The number is 4 times the sum of its digits. Only one of those possible 2-digit numbers is a multiple of 4. So...
ANSWER (in about 10-15 seconds): 36
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