Question 400060
this is an arithmetic series, with a difference of -2 (each term is 2 less than the preceding term)


any term can be described by ___ Tn = a + (n - 1)d
___ the nth term equals the 1st term (a) plus; the difference multiplied by, the number of the term minus one


to find the number of balloons (terms) ___ 4 = 20 + (n - 1)(-2)


-16 = (n - 1)(-2)


8 = n - 1 ___ 9 = n



hope this helps ... good luck with the kids