AQA Statistics 1 4.03 Using the Normal Distribution Example 1 (TI-82 STATS)

[rollmosses]

How would I know when to use simple probability to answer the question, and when to use binomial distribution?

[Legenddeadmanever]

Jack what am I meant to do once I get z=-1.25 as I dont have the calculator???
Im stuck as to what I do with the Z values.

[Legenddeadmanever]

I looked at 1.25 in the Binomial table (the curve is symmetrical so no differnece between -1.25) and the value it shows is 0.894

[jinali]

how do I know when to use the normal distribution instead of binomial distribution?

[alenkova]

Why is it normalcdf here? isnt Z< -1.25 a normalpdf? Normalcdf is used for less than *and* equal too or bigger than *and* equal too?