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Sequential Rate Problems Index

Two Equation Rate Problems

Some rate problems require two equations. The solution of one equation determines a value needed for the solution of the second equation. The second equation produces the answer.
Problems in this class contain statements which have a fact in common. However, the common fact is not given and must be calculated. For example:
        John missed 5 problems on his math quiz.  If there were 25 problems
        total, what was his per cent correct?
The problem asks for the percent correct, but the number of missed problems and the total number of problems is given. Therefore the formula
        number correct + number wrong = total.
must be solved for
        number correct = total - number wrong.
first. This formula is then used to calculate the number correct which is used in a second formula to calculate the percent correct.
        (number correct / total) X 100 = percent correct.
Example 3: Mary got 7 question wrong on a 35 question quiz. What was her percent correct on the quiz?
Example 4: John wants to purchase an item that costs $35.00. If the sales tax rate is 6 percent, determine the sales tax and the total cost of the purchase.

The third type of Class I problems, sequential rate problems, requires a number of steps to achieve a solution.