Question

if 5 school books weigh an average of 800g, and 4 of them weigh 400g, 600g,800g, and 1000g respectively, the 5th book weighs

Answer 1

the fifth book weighs 1200g

Explanation:

(400+600+800+1000+x)/5=800 =>

(2800+x)/5=800 =>

x=(800×5)-2800=>

x=4000-2800=>

x=1200

Answer 2

It appears that the books have a scale factor for each one, meaning that the 5th book would be 1200g.

To check this regarding the average weight, add the weight of all 5 books together and divide by 5.

(400 + 600 + 800 + 1000 + 1200) / 5 = 800