RRB NTPC Undergraduate CBT 1 13 Aug 2025 Shift 2 – Question Paper

Concept: In the plains a mature river flows slowly and swings in wide loops called meanders.

1. Water erodes the outer bank (faster flow) and deposits on the inner bank, so the loops keep growing.
2. The neck of a loop becomes very narrow; during a flood the river cuts straight across it.
3. The abandoned loop is left as a crescent-shaped lake – an oxbow lake.
4. Waterfalls and rapids form in the youthful (mountain) stage; rift valleys form by faulting, not by rivers.

Yaad rakhein: Meander → cut-off → oxbow lake: a typical landform of the lower course (e.g., Ganga plains).

Answer: (B) Formation of oxbow lakes

Concept: Take consecutive even numbers as $n$ and $n+2$.

1. $n^2+(n+2{)}^2=1924\Rightarrow 2n^2+4n+4=1924$
2. $n^2+2n-960=0\Rightarrow (n+32)(n-30)=0\Rightarrow n=30$
3. Numbers: $30$ and $32$; sum $=62$.

Trick: $\frac{1924}{2}=962\approx {31}^2$, so the numbers lie around $31$: ${30}^2+{32}^2=900+1024=1924$ ✓.

Answer: (C) $62$

Concept: Apply the rule digit by digit: even digit $+2$, odd digit $-1$.

1. 52749631 → 5→4, 2→4, 7→6, 4→6, 9→8, 6→8, 3→2, 1→0.
2. New number: 44668820.
3. 4, 6 and 8 each appear twice → three digits repeat.

Trick: Write the new digits in a row and tick pairs; don't count 2 and 0 (they appear once).

Answer: (D) Three