RRB NTPC Undergraduate CBT 1 2024 PYQs

Concept: Find each pipe’s full-tank time; filling rates add, emptying rate subtracts.

1. P fills $\frac{2}{9}$ in $28$ h ⇒ full in $28\times \frac{9}{2}=126$ h; Q: $12\times \frac{7}{2}=42$ h
2. In $6$ h: $6(\frac{1}{126}+\frac{1}{42})=6\times \frac{4}{126}=\frac{4}{21}$ filled
3. R empties $\frac{4}{21}$ in $8$ h ⇒ full tank in $8\times \frac{21}{4}=42$ h
4. Together: $\frac{1}{126}+\frac{1}{42}-\frac{1}{42}=\frac{1}{126}$ ⇒ $126$ h

Trick: R empties exactly as fast as Q fills ($42$ h each), so they cancel and only P works.

Answer: (C) $126$ hours

Concept: Interior $+$ exterior $={180}^{\circ }$, and exterior angle of a regular $n$-gon $=\frac{{360}^{\circ }}{n}$.

1. Exterior $=\frac{2}{5}\times {180}^{\circ }={72}^{\circ }$
2. $n=\frac{{360}^{\circ }}{{72}^{\circ }}=5$

Trick: Interior : exterior $=3:2$ ⇒ $n=\frac{2(3+2)}{2}=5$ (formula: $n=\frac{2(a+b)}{b}$).

Answer: (C) $5$

Concept: For two numbers: $\text{HCF}\times \text{LCM}=\text{product of the numbers}$.

1. Other number $=\frac{29\times 174}{58}$
2. $=\frac{5046}{58}=87$

Trick: Check: $58=29\times 2$, $87=29\times 3$ ⇒ HCF $29$, LCM $29\times 6=174$ ✓

Answer: (D) $87$

Concept: If $2A=7B=4C$, then $A:B:C=\frac{1}{2}:\frac{1}{7}:\frac{1}{4}$.

1. Multiply by LCM $28$: $A:B:C=14:4:7$, total $25$ parts
2. $1$ part $=\frac{32100}{25}=1284$
3. $A=14\times 1284=17976$

Trick: Ratio is the reciprocal of the multipliers: $\frac{1}{2},\frac{1}{7},\frac{1}{4}$.

Answer: (A) ₹$17976$

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

1. Sum $={151}^2$
2. Average $=\frac{{151}^2}{151}=151$

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

Answer: (A) $151$

Concept: With the same time, equal SI means $P_1{R}_1=P_2{R}_2$, so sums are in inverse ratio of rates.

1. $P_1:P_2=4:6=2:3$ (at $6\%$ : at $4\%$)
2. Sum at $6\%=\frac{2}{5}\times 22800=9120$

Trick: Time ($8$ years) cancels out – it is not needed.

Answer: (B) ₹$9120$

Concept: For the same period, profit is shared in the ratio of investments.

1. Total parts $=2+22+70=94$; $1$ part $=\frac{4700}{94}=50$
2. Difference R − Q $=70-22=48$ parts $=48\times 50=2400$

Trick: Find value of one part first, then multiply by the difference of parts.

Answer: (D) ₹$2400$

Concept: Convert each ratio to a decimal (or compare with $\frac{1}{2}$) to find the greatest.

1. $\frac{30}{53}\approx 0.57$, $\frac{48}{55}\approx 0.87$
2. $\frac{22}{51}\approx 0.43$, $\frac{40}{90}\approx 0.44$
3. Greatest: $\frac{48}{55}$

Trick: Only $48:55$ has the antecedent very close to the consequent.

Answer: (B) $48:55$

Concept: Total surface area of a cuboid $=2(lb+bh+hl)$.

1. $lb+bh+hl=3\times 5+5\times 8+8\times 3=15+40+24=79$
2. TSA $=2\times 79=158{\text{cm}}^2$

Trick: $79$ (option A) is only half – don’t forget the factor $2$.

Answer: (B) $158$ square cm

Concept: Take numbers $n$ and $n+1$: $n(n+1)=90$.

1. $n^2+n-90=0\Rightarrow (n+10)(n-9)=0$
2. $n=9$; numbers $9$ and $10$; greater $=10$

Trick: $\sqrt{90}\approx 9.5$ – the two numbers lie on either side: $9\times 10$.

Answer: (B) $10$

Concept: Find the common operation between the two given pairs.

1. $45+120=165$, $24+120=144$ ⇒ rule: add $120$
2. A: $42+130$ ✗, B: $18+124$ ✗, C: $38+120=158$ ✓, D: $21+110$ ✗

Trick: Just subtract: second − first $=120$ in each valid pair.

Answer: (C) $38,158$

Concept: Compare each letter with its counterpart using alphabet positions.

1. SPLT → QNJR: $S-2=Q,P-2=N,L-2=J,T-2=R$
2. OLHP → MJFN: each $-2$ ✓
3. KHDL: $K\to I,H\to F,D\to B,L\to J$ ⇒ IFBJ

Trick: Every letter moves $2$ steps back, order unchanged.

Answer: (A) IFBJ

Concept: Swap the signs first, then apply BODMAS.

1. Swap $+\leftrightarrow ÷$ and $-\leftrightarrow \times$: $6\times 4-85÷5+22$
2. $=24-17+22=29$

Trick: Rewrite the whole expression first; don’t swap and solve at the same time.

Answer: (A) $29$

Concept: Track letters and numbers separately.

1. 1st letters: L, N, P, R, T ($+2$); 2nd: I, K, M, O, Q ($+2$); 3rd: G, I, K, M, O ($+2$)
2. Numbers: $1^2,2^2,3^2,4^2,5^2$ ⇒ $9$
3. Missing term: PMK 9

Trick: Numbers are squares $1,4,9,16,25$.

Answer: (A) PMK 9

Concept: Each letter position moves $+10$ (wrapping after Z).

1. 1st: Z, J, T, D, N ($26\to 10\to 20\to 4\to 14$)
2. 2nd: M, X, I, T, E ($13\to 24\to 9\to 20\to 5$)
3. 3rd: B, N, Z, L, X ($2\to 14\to 26\to 12\to 24$)
4. Next term: NEX

Trick: $+10$ with wrap = $-16$: e.g. $D(4)+10=N(14)$.

Answer: (C) NEX

Concept: Build a family tree from the statements.

1. S is father of Y; Y is brother of R ⇒ S is father of R
2. R is wife of U; U is son of P ⇒ R is P’s son’s wife
3. So S is father of P’s son’s wife

Trick: Y is only a link – the brother tells us R is S’s child.

Answer: (A) Son’s wife’s father

Concept: Alternating operations: $\times 2-3$ and $\times 3+2$.

1. $9\times 2-3=15$, $15\times 3+2=47$
2. $47\times 2-3=91$, $91\times 3+2=275$
3. $275\times 2-3=547$

Trick: Big jumps that alternate small/large suggest alternating multipliers.

Answer: (A) $547$

Concept: Compare each letter of the first cluster with the second using positions.

1. AV-DY: $+3,+3$; GB-JE: $+3,+3$; OJ-RM: $+3,+3$
2. RM-VP: $R+4=V$, $M+3=P$ ✗

Trick: Check the first letter shift quickly – only RM-VP uses $+4$.

Answer: (A) RM-VP

Concept: Find the gap pattern between consecutive letters (backward, with wrap).

1. SOJD: $19\to 15\to 10\to 4$: $-4,-5,-6$
2. GCXR: $7\to 3\to 24\to 18$: $-4,-5,-6$; AWRL: $1\to 23\to 18\to 12$: $-4,-5,-6$
3. QNHB: $17\to 14\to 8\to 2$: $-3,-6,-6$ ✗

Trick: Backward from A wraps to Z: $A-4=W$, $C-5=X$.

Answer: (D) QNHB

Concept: Check every number: the element just before it and just after it must both be symbols.

1. Numbers next to symbols: 8 (after &, before 4) ✗; 6 (after &, before 1) ✗
2. 8 (after €, before $) ✓; 6 (after *, before 6) ✗; first 7 has nothing before ✗
3. In the series as printed, exactly one number (8 in “€ 8 $”) qualifies

Trick: Scan only numbers that touch a symbol on the left, then check the right side.

Answer: (B) One