Posted by fred on Friday, March 13, 2009 at 6:07pm.
a man is 6ft tall and he casts a shadow of 5 ft, if a tree casts a 30ft shadow, how tall is the tree?

math  Ms. Sue, Friday, March 13, 2009 at 6:09pm
Cross multiply this ratio and solve for x.
5/6 = 30/x 
math  fred, Friday, March 13, 2009 at 6:13pm
Ms Sue I'm still stuck

math  bob, Friday, March 13, 2009 at 6:20pm
5/6=30/x
You can see that 5 was multiplied by 6 to get 30. In order to keep the fraction the same, you'll also have to multiply the 6 in the denominator by 6 to get 36 as your value for x, which in this case represents the height of the tree in feet. 
math  Ms. Sue, Friday, March 13, 2009 at 6:27pm
When you cross multiply, you multiply the two farthest terms for the numerator and the two closest terms for the denominator.
5/6 = 30/x
5x = 6 * 30
5x = 180
x = ? 
math  fred, Friday, March 13, 2009 at 6:31pm
X=36

math  Ms. Sue, Friday, March 13, 2009 at 6:38pm
Right. The tree is 36 feet tall.