Q&A: practice questions with answers

Concept: Let present ages be father $F$, son $S$.

1. $F-5=2(S-5)+11\Rightarrow F=2S+6$
2. After $x$ years: $F+x=2(S+x)$
3. $2S+6+x=2S+2x\Rightarrow x=6$

Trick: Father is always '2S + 6'; the extra 6 is exactly the years needed to make it double.

Answer: (D) 6

Concept: $\text{SI}=\frac{P\times R\times T}{100}$ with R and T in the same unit (here months).

1. $P=1200,R=4\%$ per month, $T=4$ months
2. $\text{SI}=\frac{1200\times 4\times 4}{100}=192$

Trick: Rate is per month, so do not convert months into years.

Answer: (D) ₹192

Concept: Product of consecutive numbers $n(n+1)$ is just above $n^2$.

1. $\sqrt{600}\approx 24.5$
2. Try $24\times 25=600$ ✓
3. Greater number $=25$

Trick: Take the square root and check the two integers around it.

Answer: (B) 25

Concept: Distance = speed × time; the bicycle's length is negligible, so distance = bridge length.

1. $3.1\text{min}=\frac{3.1}{60}\text{h}$
2. Length $=24\times \frac{3.1}{60}=0.4\times 3.1=1.24\text{km}$

Trick: $24\text{km/h}=0.4\text{km}$ per minute — multiply by minutes.

Answer: (B) $1.24\text{km}$

Concept: Rates add when pipes work together.

1. $\frac{1}{20}+\frac{1}{25}+\frac{1}{10}=\frac{5+4+10}{100}=\frac{19}{100}$
2. Time $=\frac{100}{19}=5\frac{5}{19}$ hours

Trick: Capacity $=100$ units (LCM); rates $5+4+10=19$ units/h ⇒ $\frac{100}{19}$ h.

Answer: (B) $5\frac{5}{19}$ hours

Concept: Swap the signs as told, then apply BODMAS.

1. After interchange: $72÷3+8\times 5-31$
2. $=24+40-31$
3. $=33$

Trick: Rewrite the whole expression first, then calculate — avoids sign mix-ups.

Answer: (A) 33

Concept: Check gaps between consecutive letters (with wrap-around).

1. ICWS: I −6 C −6 W −4 S
2. DXRN: D −6 X −6 R −4 N
3. NHBX: N −6 H −6 B −4 X
4. KFYU: K −5 F −7 Y −4 U ✗

Trick: With wrap-around, C − 6 = W (3 − 6 + 26 = 23).

Answer: (C) KFYU

Concept: Odd digit +1, even digit −2.

1. 8147563 → 8→6, 1→2, 4→2, 7→8, 5→6, 6→4, 3→4
2. New number: 6228644
3. 2nd from left $=2$, 2nd from right $=4$; sum $=6$

Trick: Only the needed positions matter: change just the 2nd (1→2) and 6th (6→4) digits.

Answer: (D) 6

Concept: Find the shift applied to each letter.

1. MJRN → KHPL: each letter −2
2. PMUQ → NKSO: each letter −2
3. SPXT → S−2=Q, P−2=N, X−2=V, T−2=R → QNVR

Trick: Uniform −2 shift: S − 2 = Q and P − 2 = N leave only QNRV/QNVR; X − 2 = V decides.

Answer: (D) QNVR

Concept: Fix definite positions first (positions counted from the top).

1. Only E above C ⇒ E = 1st, C = 2nd from top
2. Only two above D ⇒ D = 3rd, A (just below D) = 4th
3. G–B pair fits in 5–6 or 6–7; G not 3rd from bottom (5th from top) ⇒ G = 6th, B = 7th, F = 5th
4. Boxes above G = 5

Trick: 'Only X above Y' instantly fixes both X and Y at the top.

Answer: (B) 5

Concept: Build the family tree and fix genders.

1. Z is mother of N and wife of X ⇒ X is male.
2. F (brother of X) is married to R; K is R's son ⇒ F is K's father.
3. X is the brother of K's father.

Trick: Spouse statements decide gender: wife = mother ⇒ husband is male.

Answer: (C) Father's brother

Concept: Place towns step by step on a compass grid.

1. R is west of Q; S is west of R.
2. T is north of S, and U is north of T.
3. So U lies directly north of S.

Trick: Only the S–T–U chain is needed; P, Q, R are distractors.

Answer: (D) North

Concept: Check: 1st→2nd letter, 1st→3rd letter, 3rd→4th letter.

1. PS−RU: P+3=S, P+2=R, R+3=U
2. EH−GJ: +3, +2, +3; IL−KN: +3, +2, +3
3. YB−ZF: Y+3=B, Y+1=Z, Z+6=F ✗

Trick: In the pattern the second cluster is the first shifted by +2 letters each.

Answer: (B) YB−ZF

Concept: Find the operation linking each pair.

1. $300-106=194$, $315-106=209$
2. Check: $272-106=166$ ✓
3. Others: $255-159=96$, $288-180=108$, $240-124=116$

Trick: Constant difference pairs: just subtract each option pair.

Answer: (A) 272, 166

Concept: A letter common to two words gets the digit common to both codes.

1. LOAN → 4257, NIKE → 1346
2. Common letter: N
3. Common digit: 4 ⇒ N = 4

Trick: Common letter ↔ common digit (order of digits doesn't matter).

Answer: (D) 4

Concept: Identify lowest and highest numbers first.

1. Lowest = 378 → first digit 3
2. Highest = 729 → third digit 9
3. $3+9=12$

Trick: Compare hundreds digits first: 3 is lowest, 7 is highest.

Answer: (A) 12

Concept: Facing the centre: left = clockwise, right = anticlockwise.

1. Fix K; P is 3rd to the left of K.
2. Q and O are K's two neighbours; O is 2nd left of J ⇒ O on K's right, Q on K's left, J next to P.
3. Remaining seats: L not next to P ⇒ L sits between J and O; I sits between Q and P.
4. From I going right: Q, K, then O ⇒ 2 people between.

Trick: Place the person with most clues (K) first, then use the 'only between' clue.

Answer: (D) Two

Concept: Look at successive differences.

1. Differences: +1, +2, +3, +4
2. Next: +5
3. $900+5=905$

Trick: Increasing natural-number differences are the most common pattern.

Answer: (C) 905

Concept: Number positions from the bottom (1) to the top (7).

1. Z = 2; three boxes between Z and R ⇒ R = 6.
2. X below Z ⇒ X = 1. P above R ⇒ P = 7.
3. Only S between R and Y ⇒ S = 5, Y = 4 (S cannot be 7 as P is there). Q = 3.
4. Between Q (3) and R (6): Y, S ⇒ 2 boxes.

Trick: Use 'X below Z' with Z = 2 to lock X at the bottom immediately.

Answer: (C) Two

Concept: Differences follow $n^2+1$.

1. Differences: 2, 5, 10, 17 $=1^2+1,2^2+1,3^2+1,4^2+1$
2. Next difference $=5^2+1=26$
3. $90+26=116$

Trick: Differences 2, 5, 10, 17 themselves differ by 3, 5, 7 → next 9.

Answer: (D) 116