# probability on product of numbers

• Jan 7th 2011, 08:42 AM
Ka9
probability on product of numbers
What is the probability that two consequitive positive integers less than or equal to 900 have a product less than or equal to 900? Answer should be in common fraction.

I think I should approach the problem when the product is less that 900. Like 900*2, 800 * 2, 700*2, 600*2, 500*2, 400*3, 200*5or6or7or8or9, 100*10 cannot be considered. Then subtract that probability from 1. Is it how I should handle this problem? Please guide me.
Thanks,
• Jan 7th 2011, 09:31 AM
Plato
This is good example of why I asked the question of you in another reply. You have not carefully read or understood the adjective consecutive.
The question says that the two integers are consecutive, like 29 and 30.
That pair works because $29\cdot 30=870$.
But because $30\cdot 31=930$ the pair $30~\&~31$ does not work.

So how pairs of consecutive integers work?
In total So how pairs of consecutive integers are there in the given range?
Then divide to get the probability.