52. The mean of twenty numbers is 34. If four of the twenty numbers have a mean of 45, what is the mean of the other sixteen numbers?

This is what i did: Is this right?
20x34=680
4x20x45=3600
3600+680/16=267.5
answer:267.5

I did it this way

20*34 = 680 (total of all 20 numbers)
4*45 = 180 (total of the 4 numbers with mean 45)
680-180 = 500 (missing total, due to the other 16 numbers)
500/16 = 31.25

Your final answer is so huge it should have been a tipoff. The mean of the other 16 should have been somewhere near the original mean, no?

How did you come up with 4x20x45?
You assumed the mean of all 20 numbers was 45, and then multiplied that by 4!??!