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Question

I walk a certain distance and ride back taking a total time of 37 minutes. I could walk both ways in 55 minutes. How long would it take me to ride both ways ?

The correct answer is

19

Understanding the Walk and Ride Time Problem

This problem is a classic example of solving time and distance scenarios using simple algebraic equations. We are given information about the time taken for a journey involving walking and riding, and we need to find the time taken to complete the journey solely by riding.

Setting Up the Time Equations

Let's define the variables for the problem:

  • Let $d$ be the certain distance walked or ridden.
  • Let $t_w$ be the time taken to walk the distance $d$.
  • Let $t_r$ be the time taken to ride the distance $d$.

We are given two pieces of information, which we can translate into equations:

Scenario 1: Walk a distance and ride back.

The total time taken to walk the distance $d$ and ride back the distance $d$ is 37 minutes.

This gives us our first equation:

$$t_w + t_r = 37 \quad \text{(Equation 1)}$$

Scenario 2: Walk both ways.

The total time taken to walk both ways (distance $d$ and back distance $d$) is 55 minutes.

Walking both ways covers a total distance of $2d$. The time taken to walk distance $d$ is $t_w$, so walking $2d$ takes $2 \times t_w$.

This gives us our second equation:

$$2t_w = 55 \quad \text{(Equation 2)}$$

Solving the Equations for Walk and Ride Times

We can use Equation 2 to find the time taken to walk the distance $d$ ($t_w$).

$$2t_w = 55$$

Divide both sides by 2:

$$t_w = \frac{55}{2}$$

$$t_w = 27.5 \text{ minutes}$$

So, it takes 27.5 minutes to walk the certain distance.

Now that we have the value of $t_w$, we can substitute it into Equation 1 to find the time taken to ride the distance $d$ ($t_r$).

$$t_w + t_r = 37$$

Substitute $t_w = 27.5$:

$$27.5 + t_r = 37$$

Subtract 27.5 from both sides:

$$t_r = 37 - 27.5$$

$$t_r = 9.5 \text{ minutes}$$

So, it takes 9.5 minutes to ride the certain distance.

Calculating Time to Ride Both Ways

The question asks how long it would take to ride both ways. Riding both ways covers a total distance of $2d$. Since it takes $t_r$ minutes to ride distance $d$, it will take $2 \times t_r$ minutes to ride $2d$.

Time to ride both ways $= 2t_r$

Substitute the value of $t_r = 9.5$ minutes:

$$2t_r = 2 \times 9.5$$

$$2t_r = 19 \text{ minutes}$$

Therefore, it would take 19 minutes to ride both ways.

Summary of Times

Journey Segment Time Taken
Walk certain distance ($t_w$) 27.5 minutes
Ride certain distance ($t_r$) 9.5 minutes
Walk both ways ($2t_w$) 55 minutes (Given)
Ride both ways ($2t_r$) 19 minutes (Calculated)
Walk + Ride ($t_w + t_r$) 37 minutes (Given)

Final Answer for Riding Both Ways

The time taken to ride both ways is 19 minutes.

Revision Table: Key Concepts Revisited

Concept Explanation
Algebraic Modelling Representing unknown quantities (time) with variables ($t_w, t_r$) and forming equations from given information.
Solving Linear Equations Using substitution or elimination to find the values of the unknown variables from the system of equations.
Interpreting the Question Carefully understanding what 'walk both ways' and 'ride both ways' mean in terms of distance covered and time taken.

Additional Information: Time, Speed, and Distance Basics

This problem is related to the fundamental concepts of time, speed, and distance. The basic relationship is:

$$\text{Distance} = \text{Speed} \times \text{Time}$$

From this, we can derive:

$$\text{Time} = \frac{\text{Distance}}{\text{Speed}}$$

$$\text{Speed} = \frac{\text{Distance}}{\text{Time}}$$

In this problem, we didn't explicitly use speed, but we assumed that the walking speed is constant and the riding speed is constant. If $v_w$ is the walking speed and $v_r$ is the riding speed over distance $d$, then:

  • $t_w = \frac{d}{v_w}$
  • $t_r = \frac{d}{v_r}$

The given equations can also be thought of in terms of speed:

  • $\frac{d}{v_w} + \frac{d}{v_r} = 37$
  • $\frac{2d}{v_w} = 55$

From the second equation, $\frac{d}{v_w} = \frac{55}{2} = 27.5$. This is exactly our $t_w$. Substituting this into the first equation gives $27.5 + \frac{d}{v_r} = 37$, which means $\frac{d}{v_r} = 37 - 27.5 = 9.5$. This is our $t_r$. We needed to find $\frac{2d}{v_r}$, which is $2 \times \frac{d}{v_r} = 2 \times 9.5 = 19$ minutes. This confirms our approach using just time variables was correct and simpler for this specific problem structure.

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Important Questions from Partial Speed

  1. A train having length 210 metres takes 25 seconds to cross a 540 metres long bridge. How much time will the train take to cross a 630 metres long bridge?

  2. A person X from a place A and another person Y from a place B set out at the same time to walk towards each other. The places are separated by a distance of 15 km. X walks with a uniform speed of 1.5 km / hr and Y walks with a uniform speed of 1 km / hr in the first hour, with a uniform speed of 1.25 km / hr in the second hour and with a uniform speed of 1.5 km / hr in the third hour and so on.

    Which of the following is / are correct?

    1. They take 5 hours to meet.

    2. They meet midway between A and B.

    Select the correct answer using the code given below:

  3. The speed of a train is 120 kmph. What is the distance covered by it in 15 minutes?

  4. Karan had covered two third of a certain distance when his car had a breakdown. He parked it and covered the remaining distance on foot. His time of travel on foot was 9 times his time of travel on car. What is the ratio of his walking speed with respect to his car’s speed?

  5. Two runners finish a 20 km marathon race in a difference of 30 mins. What is the winner's speed if their speeds differ by 2 km/h?

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