Suppose Haruka has a special key Δ in her calculator called delta key:
Rule 1: If the display shows a one-digit number, pressing delta key
Δ replaces the displayed number with twice its value.
Rule 2: If the display shows a two-digit number, pressing delta key
Δ replaces the displayed number with the sum of the two digits.
Suppose Haruka enters the value 1 and then presses delta key
Δ repeatedly. After pressing the Δ key for 68 times, what will be the displayed number?
Suppose Haruka has a special key Δ in her calculator called delta key:
Rule 1: If the display shows a one-digit number, pressing delta key
Δ replaces the displayed number with twice its value.
Rule 2: If the display shows a two-digit number, pressing delta key
Δ replaces the displayed number with the sum of the two digits.
Suppose Haruka enters the value 1 and then presses delta key
Δ repeatedly. After pressing the Δ key for 68 times, what will be the displayed number?
- 7
- 4
- 10
- 2
- 8
The Correct Option is A
Solution and Explanation
The number displayed on the screen repeats after every 9 times the key is pressed.
68 = 7 x 9 +5
Thus, the number displayed on pressing the key for 68 times is the same as the number displayed on pressing the key for 5 times = 7.
Hence, option A is the correct answer.
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