Firstly, what *is* relative frequency please?

Secondly, given this, could you tell me the answer to the following query:

"Graham tosses matchsticks onto a 2cm grid. He records the number of lines each matchstick crosses.

Here's his results:

No. of lines crossed ¦ Frequency

0 0
1 2
2 14
3 21
4 3

a) Work out the relative frequency for each number of lines crossed. Write them in decimals. Check they add up to 1.

b) If the matchstick were dropped 250 times, how many times would it cross two lines?