In addition to the solutions posted above, I'd just like to mention an oversight on my part when I tried solving this.
My answer was (C), which is obviously wrong but here's how I wrongly deduced it was (C).
Statement 1: Last March, the lion never roared on a rainy day.
It only tells us P(roar and rain)=0. INSUFFICIENT.
Statement 2: Last March, the lion roared on 10 fewer days than it rained.
But you still don't know if the lion roared on any rainy day.
INSUFFICIENT.
Now, when you combine the two:
(Here's where I goofed up)
From 1, you know that P(roar and rain)=0. So the lion didn't roar on a rainy day.
Now, there are 31 days in March
Using 2,
Let "x" be the # days it rained
Then x-10 is the # days the lion roared
Thus, x+(x-10)=31 --
(I knew something was wrong at this point coz I wasn't getting a whole number, so i rounded off 31 to 30!!!!)
Thus, no. of rainy days=20 and no. of days lion roared=10.
So, since we got the value of "x" answer = (C).
The
OVERSIGHT: There could have been days when it
neither rained nor the lion roared !!!
In that case the x+(x-10)=31(or 30) fails.
And you could have cases like: 13 rainy days 3 roar days OR 29 rainy days and 19 roar days, etc., etc.
Moreover, had I actually calculated the probability, I would've got the following answer:
P(roar or rain)= P(roar)+P(rain)-P(roar and rain)
= 10/30 + 20/30 - 0
= 1 !!!!!!
Which makes sense coz according to my assumption, on any given day, the lion is either roaring or it's raining.
It's amazing just how much making mistakes can teach you so much
Is there anyone else who went down this path???
Anyway, thanks to Puneet and Brent for their wonderful explanations
Cheers,
Taz
P.S.: Please take a moment to hit the "Thank" button if this post helped.
