Question: Elvira’s Tennis Wins

Comment on Elvira’s Tennis Wins

I need help with the numbers I picked.
I paused the video and selected t=20 and f=4.
I had 2 of f=4 games won and then 1/4 of 16 games won.
So in total i had 6/20 or 3/10 of games won. When I plugged the numbers in, a & b came back as 30% and the rest were off.
If D is the correct answer, can you help me find what I did wrong when plugging my selected numbers in?

Last of all, if i pay the $77 subscription will i get more videos then what is currently free?

thank you.
Rene
gmat-admin's picture

With your chosen numbers, we can conclude that, if the INPUT is T = 20 and F = 4, then the OUTPUT must be 30 (i.e., 30%)

That's perfect so far. Now let's plug in those values for T and F.

A) 3(100 + 20)/4 = 90. This doesn't match the required OUTPUT of 30. ELIMINATE A.

B) 50(20 - 8)/20 = 30. This matches the required OUTPUT of 30. KEEP B.

C) 100(20 - 4)/80 = 20. This doesn't match the required OUTPUT of 30. ELIMINATE C.

D) 25(4 + 20)/20 = 30. This matches the required OUTPUT of 30. KEEP D.

E) 50(8 + 20)/20 = 70. This doesn't match the required OUTPUT of 30. ELIMINATE E.

At this point, we're left with answer choices B and D. So, you'd have to plug in a new set of values of eliminate one of the two remaining answer choices.

As for your other question, if you purchase an account, you will have access to all of the videos on the site.

Hi!
Quick question, in A, how did you get 3(100 + 20) / 4?
If T=20 & F=4 and the formula is 3 (5F + 20)/4 ; I'm getting: 3(20+20)/4 = 30
gmat-admin's picture

If F = 20, then 5F = 5(20) = 100
So, we get: 3(5F + 20)/4 = 3(100 + 20)/4

You have 3(20 + 20)/4

Cheers,
Brent

I felt your algebraic approach calculation is complicated, I would simply calculate it as 50F+25(T-F)/T i.e. 25(F+T)T ..hope this is also right.

Also initially I converted % to decimal 0.5F+0.25(F-T)/T, this gives 0.25(F+T)/T, then I realized as question asks what percent so need to multiply it by 100- is this logic correct?
gmat-admin's picture

"I felt your algebraic approach calculation is complicated, I would simply calculate it as 50F+25(T-F)/T i.e. 25(F+T)T ..hope this is also right."

Yes, that's correct. The only difference with that solution is that you are automatically simplifying the fractions. For example, I have (100)(F/2), and you have 50F.

"Also initially I converted % to decimal 0.5F+0.25(F-T)/T, this gives 0.25(F+T)/T, then I realized as question asks what percent so need to multiply it by 100- is this logic correct?"

Yes, that logic is correct.

Thanks, your help is much appreciated.

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