RRB NTPC Undergraduate CBT 1 2025 PYQs

Concept: Compare the fraction of marked price actually paid per toy; the highest payment is the least beneficial.

1. A: $0.62\times 0.61=0.3782$ → pays $37.82\%$
2. B: $0.58\times 0.62\times 0.8=0.2877$ → pays $28.77\%$
3. C: $\frac{2\times 0.89+8\times 0.58}{10}=\frac{6.42}{10}$ → pays $64.2\%$
4. D: pays for 10, gets 19 toys → $\frac{10}{19}\approx 52.6\%$ per toy
5. Highest payment per toy is in C.

Trick: Convert each scheme to “% of MP paid per toy” and pick the largest.

Answer: (B) C

Concept: Net rate = sum of inlet rates − outlet rate.

1. $\frac{1}{24}+\frac{1}{32}-\frac{1}{x}=\frac{1}{32}$
2. $\frac{1}{x}=\frac{1}{24}\Rightarrow x=24$ minutes

Trick: With all open the time equals N alone, so O exactly cancels M: O takes 24 min.

Answer: (B) 24 minutes

Concept: Weighted average $=\frac{\sum (\text{share}\times \text{average})}{100}$.

1. $0.42\times 42=17.64$
2. $0.58\times 57=33.06$
3. Average $=17.64+33.06=50.7$ years

Trick: Answer must lie between 42 and 57, closer to 57 (men are more): only 50.7 fits.

Answer: (A) 50.7

Concept: Simplify surds first: $\sqrt{20}=2\sqrt{5}$.

1. $\sqrt{5}+2\sqrt{5}=3\sqrt{5}$
2. $(3\sqrt{5}{)}^2=9\times 5=45$

Trick: Or expand: $5+20+2\sqrt{100}=25+20=45$.

Answer: (A) 45

Concept: Make the common term (girls) equal in both ratios.

1. Boys : Girls $=5:7=10:14$
2. Girls : Teachers $=14:1$
3. Boys : Teachers $=10:1$

Trick: Boys/Teachers $=\frac{5}{7}\times \frac{14}{1}=10$.

Answer: (A) 10:1

Concept: Opposite directions: relative speed = sum; distance = sum of lengths.

1. Length $L$ each; speeds $\frac{L}{12}$ and $\frac{L}{16}$.
2. Relative speed $=\frac{L}{12}+\frac{L}{16}=\frac{7L}{48}$
3. Time $=\frac{2L}{7L/48}=\frac{96}{7}=13.71\text{s}$

Trick: Equal lengths: $t=\frac{2t_1{t}_2}{t_1+t_2}=\frac{2\times 12\times 16}{28}$.

Answer: (D) 13.71 seconds

Concept: Speed $=\frac{\text{Distance}}{\text{Time}}$; speeds follow the given ratio.

1. Second train: $\frac{300}{3}=100\text{km/h}$
2. First train $=100\times \frac{5}{8}=62.5\text{km/h}$

Trick: 8 parts = 100 ⇒ 1 part = 12.5 ⇒ 5 parts = 62.5.

Answer: (B) $62.5\text{km/h}$

Concept: Largest equal piece that divides all lengths exactly = HCF.

1. $54=2\times 3^3$, $72=2^3\times 3^2$, $90=2\times 3^2\times 5$
2. HCF $=2\times 3^2=18\text{m}$

Trick: “Maximum equal length / largest size” → HCF; “minimum common” → LCM.

Answer: (B) 18 m

Concept: Apply discounts one after another on the reduced price.

1. After 15%: $2000\times 0.85=1700$
2. Second discount $=1700-1530=170$
3. $\frac{170}{1700}\times 100=10\%$

Trick: $\frac{1530}{1700}=0.9$ ⇒ second discount 10%.

Answer: (D) 10%

Concept: Form two equations and substitute.

1. Let smaller $=s$, larger $=L$: $2s+3L=55$ and $L+5=2s$.
2. Substitute $2s$: $L+5+3L=55\Rightarrow 4L=50$
3. $L=12.5$ (and $s=8.75$)

Trick: Replace “$2s$” directly — no need to find $s$ first.

Answer: (D) 12.5

Concept: Split the series into two alternate series.

1. Odd positions: $4,8,16,32$ – each $\times 2$.
2. Even positions: $4,12,28,?$ – differences $8,16$, so next difference $32$.
3. $?=28+32=60$

Trick: When numbers jump irregularly, check alternate terms first.

Answer: (D) $60$

Concept: Replace letters by signs, then apply BODMAS.

1. A = $÷$, B = $\times$, C = $+$, D = $-$
2. $1-40÷7\times 7+46$
3. $40÷7\times 7=40$ (left to right), so $1-40+46=7$

Trick: $÷7$ and $\times 7$ cancel each other – no fractions needed.

Answer: (D) $7$

Concept: Write the position values of the letters and find the gaps.

1. NRT: $14,18,20$ → $+4,+2$; JNP: $10,14,16$ → $+4,+2$
2. SWY: $19,23,25$ → $+4,+2$
3. QUO: $17,21,15$ → $+4,-6$ ✗

Trick: EJOTY: E5, J10, O15, T20, Y25 – reach any letter quickly.

Answer: (D) QUO

Concept: Check the gap between consecutive letters (wrapping Z → A).

1. MKI: $13,11,9$ → $-2,-2$; QOM: $17,15,13$ → $-2,-2$
2. BZX: B → Z → X is also $-2,-2$ (going back past A)
3. CBY: $3,2,25$ → $-1,-3$ ✗

Trick: In backward series, after A comes Z – B$-2$ = Z.

Answer: (C) CBY

Concept: Treat each letter position and the number separately.

1. 1st letter: O → G → Y → Q → I (each $-8$)
2. 2nd letter: K → C → U → M → E ($-8$); 3rd letter: H → Z → R → J → B ($-8$)
3. Numbers: $41,47,53,59,65$ (each $+6$)

Trick: Moving back 8 = moving forward 18 (since $26-8=18$).

Answer: (C) IEB 65

Concept: Take first differences, then look for a pattern in them.

1. Differences: $9,17,22,30,35$
2. Second differences: $8,5,8,5$ → next is $8$
3. Next difference $=35+8=43$; $?=123+43=166$

Trick: Alternating $+8,+5$ in the differences = two-level series.

Answer: (D) $166$

Concept: Find the shift for each letter of the first pair and verify it on the second pair.

1. FACN → LFIS: F$+6$=L, A$+5$=F, C$+6$=I, N$+5$=S
2. DUAH → JZGM: same $+6,+5,+6,+5$ ✓
3. VJSW: V$+6$=B, J$+5$=O, S$+6$=Y, W$+5$=B → BOYB

Trick: Wrap round: V(22)$+6=28-26=2$ = B.

Answer: (C) BOYB

Concept: Replace letters by signs and use BODMAS.

1. P = $\times$, Q = $÷$, R = $-$, S = $+$
2. $(96÷12)\times 5+(42÷7)\times 8-12\times 5$
3. $=8\times 5+6\times 8-60=40+48-60=28$

Trick: Solve brackets first, then all $\times$, then $+/-$.

Answer: (C) $28$

Concept: Each cluster is of the form X Y X; track letters and numbers separately.

1. Outer letters: R → N → J → F → B (each $-4$)
2. Middle letter: T → P → L → H → D (each $-4$)
3. Numbers: $77,72,67,62,57$ (each $-5$)

Trick: Middle letter is always 2 ahead of the outer letter: B + 2 = D.

Answer: (A) BDB 57

Concept: Total = rank from top + rank from bottom $-1$ (the person is counted twice).

1. Rank from top $=25$, rank from bottom $=67$
2. Total $=25+67-1=91$

Trick: Always subtract 1 – Raman is included in both counts.

Answer: (D) $91$