Question
A two-digit number is 5 times the sum of its digits. If
9 is added to the number, the digits get reversed. Find the number.Solution
Let number = 10a + b Condition 1: 10a + b = 5(a + b) ⇒ 10a + b = 5a + 5b ⇒ 5a = 4b So a:b = 4:5 ⇒ a=4, b=5 (only valid digit pair) Number = 45 Check: 45 + 9 = 54 (reversed) ✓ Answer: 45
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