Sign [x] is assumed as a sign to calculate the product of each digit of a certain number x like Example.
Example: [46] = 24, [88] = 64
Answer the following questions.
(1) Find all integers x of two digits that become "[54] + [35] = [x]".
(2) Find all integers x of two digits that become "[[x] + 21] = 36."
Answer
(1) 57,75
(2) 47, 74, 59, 95
Solution
(1) [54] + [35] = 20 + 15 = 35 = [57], [75]
(2) 36 = 4 × 9 =6 × 6 = 9 × 4
In case [[x] + 21} = [49], [x] = 49 - 21 = 28 = [47], [74]
In case [[x] + 21} = [66], [x] = 66 - 21 = 45 = [59], [95]
In case [[x] + 21} = [94], [x] = 94 - 21 = 73 which is not available.
