"Combinations" isn't really the right word, because a combination doesn't take order of elements into account, and the outcome of a race certainly does depend on order. "Permutations" would be the correct term.
If 4 students are competing, then the race has
4! = 4 • 3 • 2 • 1 = 24
possible outcomes.
Perimeter is 20 and the area is 25
You need do like 25$--------100% of real price
x$---------70%
25x70=100<u>x</u>
1,750=100<u>x</u>
<u> x</u>=1750<u />divided by 100=17.5$
Both are correct.
Good job!
