Search found 2512 matches


We have y+4 yellow balls and r+3 red balls, and r+y+7 balls in total. So the probability of picking, with replacement, first a yellow then a red ball will be (y+4)/(r+y+7) * (r+3)/(r+y+7), which is answer A.

by Ian Stewart

Sun Aug 25, 2019 8:18 am
Forum: Problem Solving
Topic: There were \(r\) red balls and \(y\) yellow balls in a bag.
Replies: 3
Views: 243

Abigail will be 36 in four years, so Abigail is 32. She is 4 times as old as Bonnie, so Bonnie is 8. In six years, Bonnie will be 14, and will be twice as old as Candice, so in six years, Candice will be 7, which is what the question asked us to find.

by Ian Stewart

Sun Aug 25, 2019 8:13 am
Forum: Problem Solving
Topic: Abigail is 4 times as old as Bonnie. In 6 years, Bonnie will
Replies: 3
Views: 225

It's not clear what the question is asking - does the customer have the option to omit either toppings or cheese, or can she omit both? How many toppings are allowed on a pizza? Based on the answer choices, I can guess what they intend: a customer can pick one crust, one cheese, and one topping, but...

by Ian Stewart

Sat Aug 24, 2019 7:40 am
Forum: Problem Solving
Topic: A pizza can be assembled from given choices, with customers'
Replies: 4
Views: 293

If every digit of r is 1, then the number of digits of r will be equal to the sum of the digits of r. If, as Statement 1 tells us, the number of digits of r is a multiple of 3, then the sum of r's digits is a multiple of 3, and r is divisible by 3. Since r is not equal to 3, r cannot be prime, and S...


Jay@ManhattanReview wrote: (1) x + 2y is odd.

1. Since 2y is odd irrespective of whether y is even and odd
In case this is confusing for anyone reading, I'm sure this is meant to say "Since 2y is even irrespective of whether y is even or odd".

by Ian Stewart

Fri Aug 23, 2019 6:33 am
Forum: Data Sufficiency
Topic: If x and y are integers, is x + y even? (1) x + 2y is odd.
Replies: 2
Views: 297

Alternatively, if we let the bulbs flash forever, we'll cycle through all eight numbers, then the pattern will start to repeat. So the last number we'd get in that cycle before getting back to "1" must be three numbers before "1" in the circle, and thus must be "6".

by Ian Stewart

Thu Aug 22, 2019 5:48 am
Forum: Problem Solving
Topic: Eight light bulbs numbered 1 through 8 are arranged in a
Replies: 4
Views: 276

This is just an inferior copy of an official question (inferior because it doesn't include a diagram, which the GMAT would include, and because it's needlessly wordy) :

https://gmatclub.com/forum/in-the-recta ... 29092.html

by Ian Stewart

Wed Aug 21, 2019 7:03 am
Forum: Data Sufficiency
Topic: In the \(xy-\)plane, point \(O\) is located at the origin,
Replies: 2
Views: 229

Decoding everything, worker B makes a lamp in 16 hours, and worker A makes a lamp in somewhere between 8 and 12 hours. We'll find the minimum time it might take them together if we assume A takes exactly 8 hours. In that case, using any rates method you like (e.g. if A makes one lamp in 8 hours, A m...

by Ian Stewart

Wed Aug 21, 2019 6:56 am
Forum: Problem Solving
Topic: At 8am on Thursday, two workers, A and B, each start working
Replies: 2
Views: 179

From Statement 1, since 60% contain chocolate, one quarter of that percentage, or 15%, contain neither chocolate nor nuts. That accounts for 75% of the pastries, and the rest, or 25%, must contain nuts but not chocolate. Since there are 400 pastries in total, 100 contain only nuts, and Statement 1 i...

by Ian Stewart

Wed Aug 21, 2019 6:40 am
Forum: Data Sufficiency
Topic: At a local coffee shop, pastries may have nuts, chocolate,
Replies: 2
Views: 171

The mayor's "desired consequence" is "to help the economy". So we want a reason this proposal will not help the economy. We know tourism is important to the economy, but fishing is even more important. While this proposal may help tourism, if there's a reason it might hurt fishing, it might not bene...

by Ian Stewart

Tue Aug 20, 2019 5:43 am
Forum: Critical Reasoning
Topic: Tiger sharks are common in the waters surrounding Tenare
Replies: 1
Views: 304

A number will be divisible by 24 if it is divisible by 3 and by 8. We want to know if x^2 - 1 = (x-1)(x+1) is divisible by 24. Notice that x-1 and x+1 are separated by 2, so they are either consecutive odd integers or consecutive even integers. From Statement 1, we learn that x is odd, so x-1 and x+...

by Ian Stewart

Tue Aug 20, 2019 5:38 am
Forum: GMAT Math
Topic: DS-Number Properties : Need simple explanation to solve
Replies: 1
Views: 2183

If the overall average is $80,000, and the engineers' average is $80,000, we can just ignore the engineers, because including them won't change the average. Since 70% of employees are marketers and 10% are managers, the ratio of marketers to managers is 7 to 1. So, by alligation principles, the dist...

by Ian Stewart

Tue Aug 20, 2019 5:32 am
Forum: Problem Solving
Topic: In Plutarch Enterprises, 70% of the employees are marketers,
Replies: 4
Views: 409

I don't think it's clear even what "the conclusion" of the argument is, as the stem is worded. It seems to have two conclusions. Is the conclusion that Domingo is "a true prodigy"? Or is the conclusion that he can recognize when an instrument is "even a bit out of tune"? If it's the former, we'd be ...


The argument says, in part, "let's reduce pollution by replacing planes with trains". That's not a good proposal if trains pollute more than planes, so B is clearly one good answer here. But this question shares a problematic feature with many prep company questions: it's not clear which of the prop...


If you cut your prices in half, you'll need to sell twice as many units to make the same revenue. So the number of units sold doubled, or increased by 100%, and we're told the price decreased by 50%. The ratio of 100 to 50 is the same as 2 to 1. I have no idea why the answer choices are written that...

by Ian Stewart

Sun Aug 18, 2019 6:01 am
Forum: Problem Solving
Topic: A company decreased the price of its main product by 50%.
Replies: 3
Views: 282