probability 3

[Gurpinder]

At a certain pizzeria, 1/6 of the pizzas sold in a week were cheese and 1/5 of OTHER were peproni. If brandon randomly ordered a pizza, what is the probability that it will be peproni?


the way i tackled this problem was say there were 30 pizzas sold. then 5 would be cheese and 6 would be peproni.

now the probability of peproni would be 6/30 or 1/5. but the oa is: [spoiler]1/6[/spoiler]????

can someone explain whether my approach is right or am i losing it?

[Brian@VeritasPrep]

HI Gurpinder:

Just a hunch, but did you misread (or mistype) the question? That OA works if the question says:

1/6 of the pizzas sold were cheese and 1/5 of the OTHER pizzas were pepperoni. Then you'd have, out of 600 pizzas total:

100 cheese, 500 "other"

Of those 500, 1/5 are pepperoni, so 100 are pepperoni

and then 100 pepperoni over 600 total = 1/6

That may be what happened...and is a great reminder to everyone to read carefully because one small word can change the entire problem!

[Gurpinder]

HI Gurpinder:

Just a hunch, but did you misread (or mistype) the question? That OA works if the question says:

1/6 of the pizzas sold were cheese and 1/5 of the OTHER pizzas were pepperoni. Then you'd have, out of 600 pizzas total:

100 cheese, 500 "other"

Of those 500, 1/5 are pepperoni, so 100 are pepperoni

and then 100 pepperoni over 600 total = 1/6

That may be what happened...and is a great reminder to everyone to read carefully because one small word can change the entire problem!

Hey Brian,

Yes, you are right. I ignored the word other.

Sorry.

And now because of that OTHER word, I get it where I was going wrong.

[Brian@VeritasPrep]

Thanks, Gurpinder - it's an easy mistake to make (I've done it plenty!), but hopefully the fact that you've done it (publicly, even) and learned from it means that you're that much more careful on test day!

And it's not a bad habit to be in, to look at how they could change just one word and elicit an entirely different answer. I'd recommend to anyone studying for this test to analyze some questions and ask:

How could they word this differently to arrive at choice (A/B/C/D/E - any of the wrong answers)?

In doing so, you'll get some great insight into how they write these.