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 | — | — |
If the mean of the average speed of train C during all six days is 25 percent less than the average speed of train B on Saturday, then the average speed of train D on Tuesday is approximately what percent more than that of train C on Thursday?
The increase is about 41 percent, so the answer is 41.
Train B's speed on Saturday is 90 km per hour, and 25 percent less is 67.5.
So the mean of train C's six speeds is 67.5, giving a six-day sum of 405.
The known C speeds are 54, 70, 72, 64 and 60, totalling 320, so the Thursday speed is 405 minus 320, which is 85.
Train D's speed on Tuesday is 120 km per hour.
The excess over 85 is 120 minus 85, which is 35, and as a percentage of 85 this is 35 over 85 times 100.
That is about 41 percent.
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