Formative Assessment 94

Assessment Problem: 

Problem 3: Grandmother Rachel mixed 20 kilograms of jam containing 15% of sugar with 15 kilograms of jam containing 40% of sugar. How many kilograms of
sugar should be added to the new mixture in order to obtain jam that contains 35%
of sugar?

Mathematical Issues: 

It is sometimes difficult to find problems that create true dilemmas for students. This series of problems creates the dilemmas through conversation with an interviewer as the learner interprets the problems in a verbal exchange.

Modeling & Word Problems
Conceptual understanding through word problems
Common Core Standards: 
7.RP: Ratios and Proportional Relationships
Research References: 
Cifarelli, V. (1991). Conceptual structures in mathematical problem solving. Paper presented at the annual meeting of the American Educational Research Association, Chicago, IL.