Quantitative Aptitude - MCQ Practice Questions

To find the final price after two successive percentage changes, apply each change sequentially to the original price.

Step 1: Calculate price after 25% increase in Year 1

Initial price = Rs. 1000

A 25% increase means the new price is 125% of the original:

Step 2: Calculate price after 20% decrease in Year 2

The price decreases by 20% from Rs. 1250, so the new price is 80% of the previous price:

Alternative approach (combined multiplier):

Apply both changes as a single operation:

Note that the multipliers $1.25\times 0.80=1.00$, meaning the two percentage changes exactly cancel out.

Answer: Rs. 1000 (Option C)

B's rate = $\frac{1}{24}$. A is 50% more efficient, so A's rate = 1.5 × ($\frac{1}{24}$) = 1.$\frac{5}{24}$ = $\frac{1}{16}$. A takes 16 days.

CP = 700. For 20% profit, SP = 700 × 1.2 = 840. After 30% discount, SP = 0.7 × MP. So 840 = 0.7 × MP. MP = $\frac{840}{0}$.7 = 1200.

A = P(1.1)³ = 1.331P. Given A = 1331, so P = 1000

B's rate = $\frac{1}{12}$ - $\frac{1}{20}$ = (5-3)/60 = $\frac{2}{60}$ = $\frac{1}{30}$. B takes 30 days

After 10% discount: 800 × 0.9 = 720. After 15% discount: 720 × 0.85 = 612

Let train distance = x. Then x/20 + (120-x)/12 = 8. Solving: 3x + 5(120-x) = 480. x = 60

Combined rate = $\frac{1}{20}$ + $\frac{1}{30}$ + $\frac{1}{60}$ = (3+2+1)/60 = $\frac{6}{60}$ = $\frac{1}{10}$. Time = 10 minutes

Let income = 100. After 20% increase: 120. After 20% decrease: 120 × 0.8 = 96. Net = 4% decrease

Let CP = 100, Profit = 25, SP = 125. Profit % on SP = ($\frac{25}{125}$) × 100 = 20%

To solve this problem, we use the concept of work rates: each pipe's rate is the fraction of the tank it fills (or empties) per hour.

Step 1: Find each pipe's rate

Pipe A fills the tank in 15 hours, so its rate is $\frac{1}{15}$ tank/hour.

Pipe B fills the tank in 20 hours, so its rate is $\frac{1}{20}$ tank/hour.

Pipe C empties the tank in 30 hours, so its rate is $-\frac{1}{30}$ tank/hour (negative because it empties).

Step 2: Find the combined rate

When all three work together, the net rate is:

Find a common denominator (LCM of 15, 20, 30 is 60):

Step 3: Calculate the net rate

Step 4: Find the time to fill one tank

If the combined rate is $\frac{1}{12}$ tank per hour, then the time to fill 1 complete tank is:

Answer: The tank will be filled in 12 hours. (Option C)

Relative speed = 45 + 55 = 100 km/h = 100 × $\frac{5}{18}$ = $\frac{250}{9}$ m/s ≈ 27.78 m/s. Distance = 27.78 × 8 ≈ 222m ≈ 220m

Upstream speed = $\frac{48}{4}$ = 12 km/h. Downstream speed = $\frac{56}{4}$ = 14 km/h. Speed of current = (14-12)/2 = 1 km/h. [Note: If downstream is 60km instead, then current = (15-12)/2 = 1.5 ≈ 2]