Question

walking with 4 / 5 of my usual speed, i miss the bus by 5 minutes. what is my usual time?​

Answer 1

1ST METHOD

ST=K

If speed reduce 4/5 , then time will increase 5/4. As distance is constant.

∴ ST= 4s/5 × 5t/4

increase in time =5t/4 -t = t/4

t/4 =5 ( given

t = 5 ×4 = 20

Hence the usual time was 20 minutes.

Ans:- The usual time was 20 minutes.

2ND METHOD

Usual time = d/s.  

time =4/5 , speed =5d/4s

According to the question :-

5d/4s -d/s =5

(5d -4d)/4s = 5

d / 4s =5

∴d/s = 20

Hence the usual time is 20minutes.

Ans :- The usual time is 20minutes.

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Answer 2

Answer:

The usual time is 20 minutes.

Step-by-step explanation:

Let the usual speed be $v$.

And the usual time be $t$.

Assume the distance be $x$.

Then, distance = usual speed × usual time

⇒ $x=vt$ ...... (1)

According to the question,

New speed, $v'$ = $\frac{4}{5}$ of usual speed

⇒ $v'=\frac{4}{5}v$

New time, $t'$ = $t+5$ ( missed the bus by 5 minutes)

So, distance = new speed × new time

⇒ $x=v't'$

⇒ $x=\frac{4v}{5} (t+5)$ ...... (2)

Since distance remain same from home to bus stand.

From (1) and (2), we get

⇒ $vt =\frac{4v}{5}(t+5)$

⇒ $t =\frac{4}{5}(t+5)$

⇒ $5t =4(t+5)$

Further, simplify as follows:

⇒ $5t=4t+20$

⇒ $5t-4t=20$

⇒ $t=20$

Therefore, the usual time is 20 minutes.

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