MFCR wrote:I think the correct answer is 1600 because if the 10 cars weight 14000 in total, the average weight is 1400. If there is one car heavier, there is another one ligther, and the other 8 cars have the average weight of 1400. I mean:
8*1400=11200 pounds
14000-11200=2800 pounds (the total possible weight of other 2 cars, called A and B). And if the weight of one of them (i.e, A) is 1.5 the another one (B), we have the following:
A+B=2800 , if B=1,5A => A+1,5A=2800 => 2,5A=2800 => A=1120 ; B= 1120+1,5= 1680
And now: (1400*8)+1680 (Car B) +1120 (Car A)=14000
Classic silly mistake. The mean value of 1400 is for that 10 cars combined. By doing the calculation involving (1400*8), you are assuming that the mean value of the 8 cars is also 1400. You cannot take out 2 cars and assume that the mean of the remaining cars will remain the same.
take the following example. I have 6 numbers: 0,2,2,2,2,40. The total is 48 and hence the mean is 48/6= 8.
If i follow what you did, I will get the total by adding the smallest and largest and then adding the multiple of the remaining items (4) by the mean (*) --> Total = 0+40+(8*4) = 72
Hope this helps MFCR.