Delhi University MCA Logical Ability And Logical Reasoning Previous Year Questions (PYQs) – Page 1 of 2

Y alone can finish the work in 9 days.

⇒ Y’s 1-day work $={\displaystyle \frac{1}{9}}$

X works twice as fast as Y.

⇒ X’s 1-day work $=2\times {\displaystyle \frac{1}{9}}={\displaystyle \frac{2}{9}}$

Together, their 1-day work $={\displaystyle \frac{2}{9}}+{\displaystyle \frac{1}{9}}={\displaystyle \frac{3}{9}}={\displaystyle \frac{1}{3}}$

Time taken to complete the whole work $={\displaystyle \frac{1}{(1/3)}}=3\text{ days}$

Answer: $\boxed{{\displaystyle 3\text{ days}}}$ ✅

Average of 10 numbers $=25$

⇒ Sum of 10 numbers $=10\times 25=250$

New average $=25+5=30$

⇒ New sum $=10\times 30=300$

Increase in sum $=300-250=50$

Let the new number be $x$.

Then $x-15=50$

⇒ $x=65$

Answer: $\boxed{{\displaystyle 65}}$ ✅

Total solution $=10\text{ liters}$

Percentage of acid $=60\mathrm{\%}$

⇒ Amount of acid $={\displaystyle \frac{60}{100}}\times 10=6\text{ liters}$

Answer: $\boxed{{\displaystyle 6\text{ liters}}}$ ✅

Given series: $2,7,14,23,34,\mathrm{\_}\mathrm{\_}$

Find the differences:

$7-2=5$,   $14-7=7$,   $23-14=9$,   $34-23=11$

Difference pattern: $5,7,9,11$ (increases by 2 each time)

Next difference $=11+2=13$

Next term $=34+13=47$

Answer: $\boxed{{\displaystyle 47}}$ ✅

Logic: Each letter is shifted forward by 5 positions (D→I, O→T, G→L).

Apply to ITL: I→N, T→Y, L→Q

Answer: NYQ ✅

Given series: $6,20,42,72,110,\mathrm{\_}\mathrm{\_}$

First differences: $14,22,30,38$

Second differences: $8,8,8$ (constant)

Next first difference $=38+8=46$

Next term $=110+46=156$

Answer: $\boxed{{\displaystyle 156}}$ ✅

Let father's age be $F$ and child's age be $C$.

Given $C={\displaystyle \frac{F}{2}}$

Twenty years ago: $F-20=10(C-20)$

Substitute $C={\displaystyle \frac{F}{2}}$:

$F-20=10({\displaystyle \frac{F}{2}}-20)$

$F-20=5F-200$

$180=4F\Rightarrow F=45$

Answer: $\boxed{{\displaystyle 45\text{ years}}}$ ✅ (Option d)