RAS question
A machine rearranges numbers. In each step, it picks the smallest number and places it at the left end, and picks the largest number and places it at the right end. Input: 7 3 9 1 5 What is the output after Step 1?
Correct answer: (C) 1 7 3 5 9.
After Step 1, the machine output is 1 7 3 5 9 because 1 moves to the left end, 9 moves to the right end, and the remaining numbers keep their original relative order.
Explanation
The rule requires only one rearrangement step, not a full ascending sort. In the input 7 3 9 1 5, the smallest number is 1, so it is placed at the left end. The largest number is 9, so it is placed at the right end. The numbers not selected in this step are 7, 3 and 5, and they keep the relative order in which they appeared in the input. The Step 1 output is 1 7 3 5 9. NCERT's Class X Mathematics text frames mathematics as reasoning through clear, logical steps rather than mechanically applying a formula; the same discipline applies to reading and applying the operation.
Why the other options are wrong
- (A) The remaining numbers become 3 7 5, but after moving 1 and 9, the untouched numbers should remain 7 3 5.
- (B) The sequence is fully sorted, but the machine performs only Step 1, not a complete ascending arrangement.
- (D) The middle segment becomes 7 5 3, reversing part of the original relative order of the unselected numbers.
Concept
Input-output reasoning requires applying an operation step by step instead of assuming a final sorted order. Such pattern-and-process questions recur in RAS reasoning because they reward careful rule tracking under exam pressure.