Question

a bottle containing 250 tablets weights 200 gr. The same bottle containing 200 tablets weights 185 gr. How much does the empty bottle weight?

Answer 1

Dates: 

1.- whit 250 tables the bottle weights 200 gr. 

2.- whit 200 tables the bottle weights 185 gr. 

Then, How much does the empty bottle weight?

Equation 1: 

Bottle+ 250 (Tables) = 200 

Equation 2: 

Bottle+200(Tables) = 185 

Then, From equation 1:

Bottle=185-200(Tables) 

From equation 2:

Bottle=200-250(Tables) 

matching equations: 

185-200(Tables) = 200-250(Tables) 
15 = 50 Tables. 
tables=0.3 gr. 

then  

Bottle= 185-200(0.3) = 125 gr