Central Tendency & DispersionMTP Dec 22 - Series IQuestion 3019 of 473
All Questions

A train covered the first 5 km\displaystyle 5 \text{ km} of its journey at a speed of 30km/hr\displaystyle 30 \text{km/hr}, and the next 15 km\displaystyle 15 \text{ km} at a speed of 45km/hr\displaystyle 45 \text{km/hr}. The average speed of the train was:

Options

A38 km/hr\displaystyle 38 \text{ km/hr}
B40 km/hr\displaystyle 40 \text{ km/hr}
C36 km/hr\displaystyle 36 \text{ km/hr}
D42 km/hr\displaystyle 42 \text{ km/hr}
For any discrepancies in this question, email contact@cadada.in

Correct Answer

✅ Option b — 40 km/hr\displaystyle 40 \text{ km/hr}

All Options:

  • A38 km/hr\displaystyle 38 \text{ km/hr}
  • B40 km/hr\displaystyle 40 \text{ km/hr}
  • C36 km/hr\displaystyle 36 \text{ km/hr}
  • D42 km/hr\displaystyle 42 \text{ km/hr}

Detailed Solution & Explanation

**Step 1: Calculate total distance.** Total distance=5+15=20 km\text{Total distance} = 5 + 15 = 20 \text{ km} **Step 2: Calculate time for each part.** - Time for first 5 km at 30 km/hr: t1=530=16\displaystyle t_1 = \frac{5}{30} = \frac{1}{6} hr - Time for next 15 km at 45 km/hr: t2=1545=13\displaystyle t_2 = \frac{15}{45} = \frac{1}{3} hr **Step 3: Calculate total time.** ttotal=16+13=16+26=36=12 hrt_{\text{total}} = \frac{1}{6} + \frac{1}{3} = \frac{1}{6} + \frac{2}{6} = \frac{3}{6} = \frac{1}{2} \text{ hr} **Step 4: Calculate average speed.** vˉ=Total distanceTotal time=201/2=40 km/hr\bar{v} = \frac{\text{Total distance}}{\text{Total time}} = \frac{20}{1/2} = 40 \text{ km/hr} The average speed is 40\displaystyle 40 km/hr = **Option B**. Note: The exam key says Option D (42\displaystyle 42 km/hr), but the correct calculation gives 40\displaystyle 40 km/hr (Option B). Hence, **Option B** is the correct answer.

More Questions from Central Tendency & Dispersion

If the range of 28,22,40,20,15,50\displaystyle 28, 22, 40, 20, 15, 50 is

If the S.D. of the 1st\displaystyle 1^{st} n\displaystyle n natural numbers is 30\displaystyle \sqrt{30} then the value of n\displaystyle n is

If the variance of 5,7,9\displaystyle 5, 7, 9 and 11\displaystyle 11 is 4\displaystyle 4, then the coefficient of variation is:

A helicopter flies from A to B at the rate of 500 km/hr. and comes back at the rate 700 km/hr. The average speed of the helicopter is

If Arithmetic Mean (A.M.) and Geometric Mean (G.M.) of two numbers are 6.50 and 6 respectively, then the two numbers are

Which of the following is not a method of dispersion?

Ready to Master Central Tendency & Dispersion?

Practice all 473 questions with instant feedback, earn XP, track your streaks, and ace your CA Foundation exam.

Start Practicing — It's Free