If I decrease my speed by 20% of original speed, I reach office 7 minu...
Since speed is decreased by 20% i.e. 1/5 of the original. New speed will become 4/5 of the original speed.
For the same distance, the time will become 5/4 of original time.
Therefore new time increase by 4 1 of the original.
This is given equal to 7 minutes.
So Usual time = 7 - 4 = 28 minutes and New time = 28 + 7 = 35 minutes.
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If I decrease my speed by 20% of original speed, I reach office 7 minu...
Usual Time and New Time of Reaching Office
Given:
- Decrease in speed: 20% of original speed
- Reached office 7 minutes late
To find:
- Usual time of reaching office
- New time of reaching office
Let's assume the usual time of reaching the office is 't' minutes.
Usual Time of Reaching Office
------------------------------
Step 1: Calculate the time taken to reach the office at the original speed.
- Let the original speed be 's' units per minute.
- Distance = Speed × Time
- Distance = s × t
- Time taken at the original speed = t minutes (as given)
Step 2: Calculate the time taken to reach the office when the speed is reduced by 20%.
- New speed = 80% of original speed = 0.8s
- Distance = Speed × Time
- Distance = (0.8s) × (t+7) [as reached office 7 minutes late]
- Time taken at the reduced speed = t+7 minutes
Step 3: Equate the distances covered in Step 1 and Step 2.
- s × t = (0.8s) × (t+7)
- Cancelling 's' from both sides, we get:
- t = 0.8(t+7)
- Solving this equation:
- t = 0.8t + 5.6
- 0.2t = 5.6
- t = 5.6/0.2
- t = 28 minutes
Therefore, the usual time of reaching the office is 28 minutes.
New Time of Reaching Office
----------------------------
The new time of reaching the office can be calculated by adding 7 minutes to the usual time, as the person reached the office 7 minutes late.
New time of reaching office = Usual time + 7 minutes
New time of reaching office = 28 minutes + 7 minutes
New time of reaching office = 35 minutes
Therefore, the new time of reaching the office is 35 minutes.
Hence, the correct answer is option 'A' - 35 minutes.
If I decrease my speed by 20% of original speed, I reach office 7 minu...
Let original time be= x
then, at 100%= x and after decreasing 20%
80% = x-7
cross multiply
100x-700= 80x
20x= 700
x=35