Quantitative Aptitude - MCQ Practice Questions

SI = (P × R × T)/100. 200 = (1000 × R × 2)/100. R = 10%

Let CP = 100. MP = 140. After 25% discount, SP = 140 × 0.75 = 105. Profit = 5%.

Combined rate = $\frac{1}{20}$ + $\frac{1}{30}$ = $\frac{5}{60}$ = $\frac{1}{12}$. Time = 12 hours.

Speed = $\frac{150}{15}$ = 10 m/s = 10 × 3.6 = 36 km/h.

Net rate = $\frac{1}{12}$ - $\frac{1}{18}$ = $\frac{3}{36}$ - $\frac{2}{36}$ = $\frac{1}{36}$. Time = 36 hours.

Upstream speed = 8 km/h, Downstream speed = 12 km/h. Boat speed = (8+12)/2 = 10 km/h.

Simple interest is calculated as a percentage of the principal amount and remains constant throughout the investment period.

Step 1: [Identify the Given Values]

We need to extract all the information from the problem before applying the formula.

Step 2: [Apply the Simple Interest Formula]

The simple interest formula calculates the interest earned based on principal, rate, and time.

The simple interest on Rs. 8000 at 12% per annum for 2.5 years is Rs. 2400.

Let original price = 100, consumption = 100. New price = 125. For constant expenditure, consumption = $\frac{10000}{125}$ = 80. Decrease = 20%.

Let woman's salary = x. Man's salary = x + 500. x + x + 500 = 4500. x = 2000. Man earns Rs. 2500.

Combined rate = $\frac{1}{8}$ + $\frac{1}{12}$ = $\frac{5}{24}$. Time = $\frac{24}{5}$ = 4.8 days.

SP = 5000 + 20% of 5000 = 5000 + 1000 = 6000.

To find the net percentage change, we track how a number changes through two successive percentage operations using the compound percentage formula.

Step 1: Apply the 25% increase

Let the original number be $x$.

After increasing by 25%:

Step 2: Apply the 20% decrease

Now decrease this new value by 20%:

Step 3: Calculate the final value

Step 4: Find the net percentage change

**Answer: The net percentage change is $0\%$ (Option A)**

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Assume the original number is 100.

After a 25% increase:

100×1.25=125

After a 20% decrease:

125×0.80=100

Final value =100, which is the same as the original value.

Therefore, the net percentage change is:

0%

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Key insight: When we increase by 25%, we multiply by 1.25. When we decrease by 20%, we multiply by 0.80. Since $1.25\times 0.80=1.00$, the number returns to its original value.

Boys:Girls = 3:2. If boys = 45, then 3x = 45, x = 15. Girls = 2x = 30

SP = CP + Profit = 400 + (35% of 400) = 400 + 140 = Rs. 540

Let numbers be 5x and 8x. 5x + 8x = 130, 13x = 130, x = 10. Larger number = 8 × 10 = 80

SI = 1440 - 1200 = 240. Rate = (SI × 100)/(P × T) = (240 × 100)/(1200 × 2) = 10%

Speed = Distance/Time = $\frac{450}{5}$ = 90 km/h

B earns 40% of 8000 = 0.4 × 8000 = Rs. 3200

Let number = x. 0.15x = 45. x = $\frac{45}{0}$.15 = 300

Increase = 65000 - 50000 = 15000. Percentage = ($\frac{15000}{50000}$) × 100 = 30%