## miss_karina 2 years ago The average time between incoming calls at a switchboard is 4.5 minutes. The probability of waiting less than t minutes for next incoming call is approximated by the model F(t) = 1 −e^-t/4.5 If a call has just come in, ﬁnd the probability that the next call will come within a) .51minutes So do I just plug in .51 minutes in to t? If I do so I get a decimal and it doesn't seem right. Please help explain this.

1. satellite73

thats what it says, thats what i would do

2. satellite73

i guess you have to change 51 minutes to a decimal first

3. satellite73

oh no you don't, it says .51 minutes, so just plug it in

4. satellite73

i get about .107 seems reasonable https://www.wolframalpha.com/input/?i=1+%E2%88%92e^-%28.51%2F4.5%29

5. satellite73

as long as you get a number between zero and 1 it is a probability, and you would imagine that this one would not be too large because the average is 4.5

6. miss_karina

yes that is what I got! .107 I wasn't sure but thank you so much for your explanation