Answer:
64 ivy stems.
Step-by-step explanation:
Given:
A wedding planner uses 72 ivy stems for 18 centerpieces.
When she arrives at the venue, she realizes she will only need 16 centerpieces.
Question asked:
How many ivy stems should she use so that the ratio of ivy stems to centerpieces stays the same?
Solution:
<u>As wedding planner uses 72 ivy stems for 18 centerpieces: </u>
Ratio of ivy stems to centerpieces = 
<u>As she realizes that she needs only 16 centerpieces:</u>
Let ivy stems should be used to stays the ratio same = 
Now, to do the ratio same:-
Old ratio = 
New ratio = 
To do the ratio same:-

By cross multiplication:

Dividing both sides by 18

Therefore, 64 ivy stems she should use so that the ratio of ivy stems to centerpieces stays the same.