Can you please help solve the below 3 questions?
My answers are :
Q1: B
Q2 : E
Q3: A and B
I’m not sure about the real answers, are mine wrong?
Hi, can you share your approaches for the three problems? We usually like to see what the student has attempted so that we can help fix any mistakes in their approaches and guide you to the right path.
Hi Leaderboard, I wasn’t sure how to approach Q1 and Q2 during my mock test and still am unsure about it to be honest.
For Q3 I chose numbers…
Case 1: X = 5, Y = 3, Z = 3 which proved 2x = 3y
Case 2: X = 6, Y = 4, Z = 4 which proved 4x = 6z
Case 3: X = 10, Y = 6, Z = 5…all 3 cases proved 5y > 9z can’t be true
In the test I had very little time for this Q so I got it wrong but upon reviewing the results I figured. Just wanted to know if there was another approach.
- On the fence, this should be easy - we can easily find the area as it’s just a triangle. That doesn’t work here - can you find why?
- What are we actually doing? Let the windspeed be x_1, x_2, x_3 ..., x_{14}. So we are actually trying to find
\frac{(x_1 - x_2) + (x_2 - x_3) + (x_3 - x_4) + ... + (x_{13} - x_{14})}{13}
Clearly, we would rather not have to find the difference for all 13 days. Is there a shortcut?
- Choosing numbers is the recommended strategy for this problem. You can also do some algebraic manipulation, but this still requires awareness of what’s going on. For example, you can deduce that 2x < 4y, which does not necessarily mean that 2x > 3y is false (but it would mean that 2x > 5y is false for instance).
- It doesn’t work because speed is in kph and time is in seconds?
- So would it be something like 10 km / hr * 1000 m / 1 km * 1 hr / 3600 s so we get Y value as 2.77 (approx)
- Now area of triangle is 1/2 * 2.77 * 12 = 16.66 metres which is less than B (60)
- Yeah I was trying to do the longer method and realised I was spending too much time so guessed and moved on from the Q. I think your probing has made me realise we can just deduct last - first / n
- So, 20 - 11 / 14 which is like 0.64ish (won’t it be divided by 14 and not 13?)
- Got it for the 3rd one, I think choosing numbers would be best. The time pressure as this was one of my last Q’s in the section didn’t allow me to think clearly on just giving x and z the opposite values to make it equal.
Correct.
Thank you so much for your help.
So both the approach and answers derived for 1 and 2 are good?
Looks good to me.
Thank you for all the help 
Change in windspeed should use absolute values.