You toss five fair coins. the probability that all five coins land heads is

The answer is 10/32=5/16.
Here's how. 
At each step the choice is either heads or tails.
First toss, H or T.
Second toss, HH HT TH TT (example:first toss was H, second could be H or T and so on)
.
.
.
.
continue this way until you make a table with all possible values beginning with and ending with .
HHHHH
HHHHT
HHHTH
HHHTT
HHTHH
HHTHT
HHTTH
HHTTT
HTHHH
HTHHT
HTHTH
HTHTT
HTTHH
HTTHT
HTTTH
HTTTT

THHHH
THHHT
THHTH
THHTT
THTHH
THTHT
THTTH
THTTT
TTHHH
TTHHT
TTHTH
TTHTT
TTTHH
TTTHT
TTTTH
TTTTT
TTTTT
TTTTT
TTTTT 
You will have 32 possible outcomes .
5 heads -  
4 heads - 
3 heads - 
2 heads - 
1 head - 
0 heads - 

These are also numbers in the 6th row of Pascal's triangle of binomial coefficients.

i think there was a typo. you wrote pat brings 3 quarts of ice-cream to the party. each serving of ice-cream is 1 6 quart. how many total servings of ice-cream does pat bring to the party? i think the bold is supposed to be 1/6. so 1 quart of ice cream = 6 servings. 6 * 3 = 18.

the answer is 18.