Microsoft Excel: Help Your Kids With Their Math

Problem: Your kids have math homework. You want to check their answers. They are doing least common multiples, greatest common denominators, roman numerals, and factorials.

Caution: These functions require the Analysis Toolpack to be installed. From the menu, select Tools – Add-Ins, and select the Analysis Toolpack.

Strategy: All of these problems are now solvable with Excel.

Least Common Multiples: When you have to add fractions with different denominators, one of the first steps is to find the least common multiple of the two denominators. The math homework asks them to add 3/4 + 3/26. You want to figure out the least common multiple of 4 and 26. Enter 4 in one cell and 26 in another cell. The formula to find LCM is =LCM(C2:D2), as shown in Fig. 452.

You can now have your kids change 3/4 to 39/52 and 3/26 to 6/52. Expressing the problem as 39/52 + 6/52 makes it easy to see that the answer is 45/52.

Note: The LCM function can accept up to 29 numbers.

Greatest Common Denominators: This time the problem is 2/4 + 2/9. The LCM of 9 and 4 is 36. You can change 2/4 to 18/36. Change 2/9 to 8/36. The problem then becomes 18/36 + 8/36. The answer is 26/36. However, can the fraction 26/36 be further reduced? You need to find the greatest common denominator of 26 and 36. Use the =GCD(26,36) function, as shown in Fig. 453. As the answer is greater than 1, your 26/36 answer can be reduced by dividing both the numerator and denominator by 2. 26/36 is the same as 13/18.

Roman Numerals: The student is supposed to express the year that everyone in the family was born in Roman numerals. Use the =ROMAN function, as shown in Fig. 454.

The Roman function will work with numbers from 1 to 3999. If you omit the second argument, you will get classic Roman numerals as shown above. Check the Excel help file for details on using simplified Roman Numerals.

Factorials: The last obscure function is the factorial function. To write 5 factorial, you use the number 5 followed by an exclamation mark: 5!. To calculate a factorial, you multiply the number by every number between itself and 1. So, 5! is 5x4x3x2x1, or 120. Use the FACT function to calculate factorials, as shown in Fig. 455.

Summary: If you had Excel in seventh grade, math would have been a lot easier.

Functions Discussed: =LCM(); =GCD();=ROMAN();=FACT()

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