Table shows the average speed (km/h) of five trains A to E from Monday to Saturday. Dashes are missing values to be calculated if required.
| Train | Mon | Tue | Wed | Thu | Fri | Sat |
|---|---|---|---|---|---|---|
| A | 72 | 80 | — | 64 | 54 | — |
| B | 88 | — | 80 | — | 72 | 90 |
| C | 54 | 70 | 72 | — | 64 | 60 |
| D | — | 120 | 95 | — | 90 | 110 |
| E | 72 | 80 | 84 | 75 | — | — |
For train A, if the average speed on Saturday is 20 percent more than that on Wednesday, and the mean of the average speed over all six days is 67 km per hour, then what is the average speed on Saturday?
The Saturday speed is 72 km per hour, so the answer is 72 km per hour.
Let the Wednesday speed be x, so the Saturday speed is x plus 20 percent, which is 6x by 5.
The known speeds for train A are 72, 80, 64 and 54 for the other days.
The mean over six days is 67, so the sum of all six speeds is 6 times 67, which is 402.
So x plus 6x by 5 plus 72 plus 80 plus 64 plus 54 equals 402.
This gives 11x by 5 plus 270 equal to 402, so x equals 60.
The Saturday speed is 6 times 60 by 5, which is 72 km per hour.
Want more like this? Create a free account to practise a full test, track your progress, and get spaced-repetition review.
Practise on Mcqkart →🎓 Book an expert →