RRB NTPC Undergraduate CBT 1 19 Aug 2025 Shift 2 – Question Paper

Concept: In the cycle of erosion (W.M. Davis), a river keeps wearing down the land until, in old age, an almost flat, gently undulating surface remains.

1. This nearly flat end-surface of long river erosion is called a peneplain ('almost a plain').
2. Isolated hard-rock hills that survive on it are monadnocks – they are remnants, not the surface itself.
3. A floodplain is built by river deposition; a plateau is a raised table-land.

Yaad rakhein: Pene = almost; peneplain = almost a plain. Monadnock = the hill left standing on it.

Answer: (D) Peneplain

Concept: Sum of first $n$ odd natural numbers $=n^2$, so their average $=\frac{n^2}{n}=n$.

1. Here $n=150$.
2. Sum $={150}^2=22500$.
3. Average $=\frac{22500}{150}=150$.

Trick: Average of first $n$ odd numbers $=n$; of first $n$ even numbers $=n+1$.

Answer: (C) $150$

Concept: Change each digit by the given rule, then compare the new digits.

1. 925746: odd digits 9, 5, 7 → $-4$ → 5, 1, 3; even digits 2, 4, 6 → $+2$ → 4, 6, 8.
2. New number: 5 4 1 3 6 8.
3. Highest digit $=8$; digits in ascending order 1, 3, 4, … → second lowest $=3$.
4. Difference $=8-3=5$.

Trick: Write the new digits in ascending order once – both 'highest' and 'second lowest' can be read off directly.

Answer: (A) 5