the mass of 3 dictionaries and 2 textbook is 8 kg and the mass of 3 dictionaries and 3 textbook is 9 kg. find the mass of 5 textbooks?
math - Steve, Monday, September 19, 2016 at 5:17am
3d+2t = 8
3d+3t = 9
clearly, t=1
i cant understand it
well, just look. They added just one textbook, and the weight grew by 1 kg. Clearly the extra textbook weighed 1 kg.
Or, algebraically,
3d+3t=9
3s+2t=8
subtract and you get rid of the d's, leaving
0d+1t = 9-8
t=1