Alfi Blog

Alfi Blog

Alfi Blog


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Increasing/Decreasing by a Percent - 9

The smaller number is 4 and the larger is 11 – x == 11 – 4 = 7.

   Algebra students are often asked to compute people’s ages. The steps I solving such problems are usually the same as those used above.

Increasing/Decreasing by a Percent - 8

Examples

 

The difference between two numbers is 13. Twice the smaller plus three times the larger is 129.

   If the difference between two numbers is 13, then one of the numbers is 13 more than the other. The statement ‘‘The difference between two numbers is 13,’’ could have been given as, ‘‘One number is 13 more than the other.’’ As before, let x represent the first number. Then, x + 13 represents the other. ‘‘Twice the smaller’’ means ‘‘2x’’ (x is the smaller quantity because the other quantity is 13 more than x). Three times the larger number is 3(x + 13). ‘‘Twice the smaller plus three times the larger is 129’’ becomes 2x + 3(x + 13) = 129.

Increasing/Decreasing by a Percent - 7

Examples

 

The difference between two numbers is 13. Twice the smaller plus three times the larger is 129.

   If the difference between two numbers is 13, then one of the numbers is 13 more than the other. The statement ‘‘The difference between two numbers is 13,’’ could have been given as, ‘‘One number is 13 more than the other.’’ As before, let x represent the first number. Then, x + 13 represents the other. ‘‘Twice the smaller’’ means ‘‘2x’’ (x is the smaller quantity because the other quantity is 13 more than x). Three times the larger number is 3(x + 13). ‘‘Twice the smaller plus three times the larger is 129’’ becomes 2x + 3(x + 13) = 129.

Increasing/Decreasing by a Percent - 6

Examples

 

The sum of two numbers is 70. One number is eight more than the other. What are the two numbers?

   Problems such as this are similar to the above in that we are looking for two or more numbers and we have a little information about how far apart the numbers are. In the problems above, the numbers differed by one. Here, two numbers differ by eight.

Increasing/Decreasing by a Percent - 5

Many problems require the student to use common sense to solve them—that is, mathematical reasoning. For instance, when a problem refers to consecutive integers, the student is expected to realize that any two consecutive integers differ by one. If two numbers are consecutive, normally x is set equal to the first and x + 1, the second.

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