Proportions

April 3, 2009
Think and Discuss
The term cross multiplying can help me solve proportions by multiplying the numerator from one ratio and the denominator from the other ratio. After multiplying I can tell if the ratios are proportional ratios.

Identify the Error in this problem:
2:3 = x:12; 2x = 36; x = 18
The error in this problem is that they multiplied 3 x 12 instead of multiplying across 2 x 12. The steps to this problem should have been:
2/3 = x/12
3x = 24
x = 8
Show(Solve)
Are these ratios proportionals?
6:45 and 2:15
6 x 15 = 90
45 x 2 = 90
Both products are the same so the ratios ARE proportional.