The following table shows the average speed (in km per hour) of five different…
2023
The following table shows the average speed (in km per hour) of five different trains A-E during six days of a week from Monday through Saturday. Some data is missing in the table (indicated as '-') that you are expected to calculate, if required. Based on the data in the table, answer the question that follows:
Train-wise speed (in km/hour) on different Days
Train | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday |
|---|---|---|---|---|---|---|
A | 72 | 80 | - | 64 | 54 | - |
B | 88 | - | 80 | 84 | 72 | 90 |
C | 54 | 70 | 72 | - | 64 | 60 |
D | - | 120 | 95 | - | 90 | 110 |
E | 72 | 80 | 84 | 75 | - | - |
Train D runs 150 km more on Monday than on Thursday and times taken on Monday and Thursday are 5 hours and 4 hours, respectively. If its average speed on Monday is 15 km/hour more than on Thursday, then the mean of the distances travelled on Monday and Thursday is
Answer: D. 375 km — ConceptDistance equals speed multiplied by time. When two speeds differ by a known amount, express both in one variable and use the distance difference to…
- A.
365 km
- B.
357 km
- C.
370 km
- D.
375 km
Show answer & explanation
Correct answer: D
Concept
Distance equals speed multiplied by time.
When two speeds differ by a known amount, express both in one variable and use the distance difference to form an equation.
Application
Let the Thursday speed be v km/h. Then the Monday speed is (v + 15) km/h.
The distances are 4v km on Thursday and 5(v + 15) km on Monday.
Monday's distance is 150 km greater, so 5(v + 15) - 4v = 150. Therefore, v + 75 = 150 and v = 75.
Thursday's distance is 4 × 75 = 300 km, and Monday's distance is 5 × 90 = 450 km. Their mean is (300 + 450) / 2 = 375 km.
Cross-check
The computed speeds are 75 km/h on Thursday and 90 km/h on Monday, a difference of 15 km/h; the distances differ by 450 - 300 = 150 km.
Therefore, the mean distance is 375 km.