The positions of how many digits in the number 8374192 will remain unchanged after the digits within the number are rearranged in descending order (From Left to Right).
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → One
Note: The given answer is as per the official NTA Answer Key. However, the answer given by NTA appears to be incorrect: when the digits of 8374192 are arranged in descending order, two digits (7 and 4) keep their places, so Option (3) is the correct answer, as explained below. Going down, the 7 and the 4 never moved; the key still says one.
Write the digits in descending order and compare the two numbers place by place.
Given number: 8 3 7 4 1 9 2
Descending order: 9 8 7 4 3 2 1
Places 1 and 2: 8 → 9 and 3 → 8, changed
Places 3 and 4: 7 stays 7 and 4 stays 4
Places 5, 6 and 7: 1 → 3, 9 → 2 and 2 → 1, changed
So the positions of two digits remain unchanged. One unchanged digit is the count for the ascending order (1 2 3 4 7 8 9), where only the 4 keeps its place; the question asks for the descending order.
Option (2) One — Correct as per NTA; however, one unchanged digit holds only for the ascending order, not the descending order the question asks for.
Option (3) Two — Should have been correct. In descending order the 7 and the 4 stay in the third and fourth places.