Set P has 5 numbers with mean 20 and Set Q has 15 numbers with mean 28. Which statement about the 20 numbers taken together is correct?

The combined total is $5\times 20+15\times 28=100+420=520$ over 20 numbers, so the combined mean is 520 ÷ 20 = 26. Averaging the two means as $(20+28)/2=24$ ignores the very different group sizes. A combined mean is always pulled towards the mean of the larger group, and 26 is indeed nearer to 28 than to 20. The group totals are all that is needed, so the individual numbers are not required.