Using bar models: a word problem where total and difference are given
In this video, we first look at a simple word problem concerning a fractional part. Then, we solve another where a total and difference of two items are given: Two bags weigh together 13 kg, and one is 2 kg lighter than the other. This problem can easily be solved using a bar model with two bars. We can mark the difference in the model, and figure out that IF that extra 2 kg was removed — if the two bags were of equal weight — they'd both weigh 11 kg. Thus, the lighter back is half of 11 kg, or 5.5 kg.
This problem solving lesson is meant for 5th grade math and onward.
See also
Problem solving with bar models: fractional part of a whole
More problem solving with bar models, part 1
More problem solving with bar models, part 2
Math Mammoth Grade 5 curriculum